Front Seat Adjustment Mechanism
As the seats come to you, there is paint inside the tracks that are part of the airframe, both the channels at the rear of the seat and the “ears” at the front. This paint should be sanded out to ensure smooth operation. Also, the “ears” may need a little tweaking to make sure there is sufficient clearance for the seat rails because they sometimes pull in while being welded.
Installing the seats is pretty obvious, but the locking pin mechanism requires a little study. There are two variations of the seat lock mechanism. Early airplanes have an ear welded to a sleeve that clamps to the tubing sticking down under the seat. The later version has the ear welded to the tube under the seat. The ear faces forward.

The T-shaped handle faces forward under the seat and pivots on the ear and presses down on a fender washer bolted to the bottom of the shaft. Put a hardware store spring in between to provide tension. There are two lengths of T-handles, the short one goes under the right seat, to clear the flap mechanism.

This is the way the seat latch looks from the front, when assembled. The short “T” handle goes under the right seat to clear to the flap handle. Drill holes in the track on 1” intervals.

There are several ways you can go about making up the cushion supports, but the way that we find most effective and lightweight is to use the same type of fabric you would use on the exterior of the fuselage. The human form is pretty blunt where it hits the seat, not a lot of sharp corners usually. Plus the cushion is between you and the support platform. For that reason, using Dacron and fabric glue, like PolyTac, is absolutely up to the task and it is the lightest way to suspend the flight crew. When it comes to cabin furnishings in general, beware, upholstery is dead weight and detracts from performance, so make it light. Also, don’t run upholstery over outside edge of seat as clearances are very tight.

Foam for Padding
Almost any type of foam can be used on the back but on the bottom. A memory foam such as
“Temperfoam” be used. It weighs a little more but has better shock absorbing capability. When building the seat cushions remember that this is where you fine tune the seating position to suit the leg length and sitting height of you and your passengers, so have the rudder pedals in place before doing the seat cushions. Regardless of the type of foam you use, a good tool for shaping is a kitchen electric carving knife like those intended for slicing a giant ham. Some foams can also be shaped with aggressive sandpaper in a power sander, but practice on some scraps first.

Installing the Back Seat
The back seat is secured to the floor by four special bolts supplied with the kit. Some kits have specially-made bolts with thick tabs welded to the top. Some use eye bolts. These thread into the four bushings welded in the floor. In early kits, these holes in the fuselage must be tapped (threaded) for the bolts. Later kits are already tapped. There are two different sizes of bolts used, 3/8 in the back, and 5/16 in the front. If you’ll be tapping the holes, run a drill bit of the proper size (Letter I and Letter Q) for the 5/16×24 and 3/8×24 taps. Approach the tapping operation carefully and with a lot of patience because getting in a hurry will result in a broken tap, which isn’t easy to remove. Keep in mind that you’ll never break a tap as long as the top of the tap and the bottom of the tap are rotating at the same speed. The bushing has been welded on, which causes it to be harder in some areas than others and where it is hard, it can be very hard, and will resist the tap. So proceed slowly. The key to success is lots of cutting oil and a tapping method where you turn the tap only 90 degrees at a time and back it up 45 degrees after each rotation. If you stick to this, you’re very unlikely to break a tap. Don’t yield to temptation and try to speed it up or force it.
The rear seats can be cross-bolted into position or, if you plan on removing them often, use “pit pins,” those are usually T-shaped pins with a push button in the middle that retracts two balls in the pin allowing it to be withdrawn. These pins are available from B&B in Kansas.
More pictures courtesy of Dave: