Note: you can’t permanently install the fuselage until the fabric is on, because at the top of the windshield the fabric wraps around into the channel.

The holes you’ll drill for the mounting tabs are the only holes you’ll drill in the windshield. Later, when you’re attaching fairing strips, none of those screws go into the windshield.

The original Bearhawk arrangement was to use a Cessna 170 windshield that was substantially trimmed to fit the Bearhawk. At some point along the line, a kind builder sent his trimmed windshield to the windshield manufacturer, and the “Bearhawk” windshield was born. You may find that the windshield needs some minimal trimming. If it does, use a rotary abrasive disk, and not any kind of saw, especially not one that reciprocates.
Leave the protective plastic covering on the windshield until the last minute, but don’t leave it somewhere where it can get hot, because the plastic covering has been known to become seriously stuck to the windshield and hard to remove.
In order to install the windshield, you’ll need to have completed the boot cowl, and it is best to wait until the wings are also mounted. The top corners of the windshield should flow right into the wing roots and without the wings you have nothing to reference to, so there’s the chance the alignment won’t be quite right and your windshield/wing fairing will look funky.
If circumstances require you to fit the windshield without the wings in place, you can use drawing number 7 from the plans (the airfoil mylar) and make a dummy root rib out of plywood. Then spend some time measuring your wings getting the exact dimension from the front of the wing fittings to the nose of the wing. Also see exactly how far the wing mount bolt hole is from the rib. You can make up a wood jig that holds the plywood rib in position where the wing would be and build the windshield to that.
Check and double check your dummy rib against the wings and the fuselage to make sure you have it in the right place. It’s safer to wait until the wings are in place to make sure you get it right.
Installing the windshield isn’t particularly difficult, but it is an expensive, one-piece, high visibility part that is easy to damage. It can be tedious because the generally brittle nature of the material, which demands that you make haste very slowly. It’s easy to scratch or crack it, so think of the cost and fragility every time you approach it.
You’ll need a 1/4” plexiglass drill bit and some extra sanding wheels for your angle head grinder. Don’t yield to temptation and try to drill plexi with regular bits. If they grab, you’ll be ordering another windshield.
The top of the windshield should slide into the channel at the top of the fuselage. On the aft vertical sides of the windshield, the acrylic goes outside of the tabs on the fuselage. The bottom tab won’t be used because the windshield doesn’t go down that far.
Trimming to fit
First, choose a good work environment. Don’t work when the shop is cold, because the acrylic will be more brittle. There is so little trimming needed that it could all be done with a handheld file. If you find you need more trimming, consider the abrasive wheel in an pneumatic angle grinder, or if you have lots of material to remove and are feeling lucky, a 60 grit flapper wheel on a 4” angle head grinder.
The procedure is literally a “cut and try” operation. Sit it up in place and see how high the back of it is above the channel in the back. Make sure you don’t lean it back to make it hit the channel and, in so doing, change the line of the windshield to the cabin roof. If should flow smoothly over the top. This is decided by eye. The amount it sits above the channel tells you how much it needs to come down and most of that will come out of the front middle at the bottom. Slowly grind away material until you get it set vertically, then tackle the horizontal (back) trimming, if any is required. Quite often little or none is required. Do your trimming very, very slowly. Lay a marker flat on the sheet metal and slide it around the sheet metal against the plexi. It’ll leave a mark that exactly follows the surface, but 1/4” or so up. You don’t want to cut to that line, but you do want to parallel it, so make a similar line about 1/16” up from the edge of the plexi and grind to that mark. Then put it on the airplane and see how it fits. Then make another mark 1/16” up from that edge. Try it out. Keep doing this process until it fits.
Take your time. Building the airplane is going to take a long time, but you’re going to keep it and fly it much, much longer than that, so there’s no reason to rush.
You’ll notice, as you’re trimming, that there are large gaps at the bottom rear corners where the instrument panel hits the side tubing. Don’t worry about those. They are covered by the fairing strip you’ll be fabricating.
Drilling the Mounting Holes
Use a bit designed for acrylic for all initial holes. Existing holes can be enlarged with a step drill. In both cases, spin the bit fast, and feed the bit very slowly. Let the bit generate some heat and slowly worry its way through the acrylic rather than actually cutting. This is a very iffy operation and the slower feed, the better you’ll be. It is suggested that you paint stripes or something on the shanks of your acrylic bits as soon as you get them so you can’t possibly pick up the wrong bit later on.
The only fasteners holding the windshield to the airplane are the screws at the side tabs, which are plenty. However, there’s a procedure to be followed when drilling those holes. We recommend that the holes in acrylic should be larger than the screws going through them to give room for thermal expansion and contraction, and to keep vibration from causing cracks because the acrylic is touching a screw shank. For example, use 1/4” holes but #8 screws. When you’re all done, if you have a screw that’s not in the middle of the hole but is touching the edge, use a round file (the kind used for sharpening chain saws) to open the hole up a little. You can bush the screws with rubber tubing to fill the holes, if desired.
Drill #30 guide holes in the steel tabs first with a regular bit. Then mount the windshield. With the windshield in position (hold it with lots of tape and/or an assistant), using a 1/8 acrylic bit, match drill a 1/8 hole through the plastic from inside, using the tab holes as guides. Use very little pressure and let the bit grind its way through. Hold a block of wood on the outside to back it up to prevent flexing and to keep the drill from slamming forward, when the bit breaks through. As you feel it starting to come through the plastic, ease off the drill pressure.
Remove the windshield and bring the holes in the windshield up to 1/4” using the acrylic bit or finely-incremented step drill, and moving slowly. After all the holes are drilled, come back with a 3/8” conventional bit and lightly twirl it in your fingers to debur/chamfer the edges of each hole in the windshield to remove stress risers.
Open the holes in the steel tabs up to 3/16 using a regular bit.
Center Supports
The plans call for an angled strip that runs around the inside of the windshield at the bottom to keep it from moving backward under air load. It doesn’t need to be a continuous strip, though you can make one if you are handy with a shrinker and stretcher. Three pieces of .032 bent to match the windshield angle, three inches long each with one inch legs and distributed across the center of the windshield will more than do the job. This photo shows a longer strip:

Bend the back-up aluminum so it exactly matches the slope of the windshield and the panel top. Be sure to round the corners and smooth the edges. Also bond thin rubber to the front surface or tape it so there is a chaffing surface to protect the windshield. These angle pieces are attached only to the boot cowl; they rest on the inside of the windshield. Drill the holes in the lower flange of the angles and snuggle them up against the back edge of the inside of the windshield. Mark the hole position in the boot cowl (top of the panel). You can’t drill the holes until you remove the windshield. Use #8 screws and nutplates to mount. Put nutplates inside the instrument panel top to receive these screws.
You’ll later create fairings to close the gap between the wing root and the fuselage, which is why the location of the windshield relative to the wing leading edge is important
Gaps can be sealed with 3m caulk sticks.