I can't take credit for the idea. That goes to Harry Baldwin and one or two other friends.

I started with about a third of a sheet (4' x 8') of one-inch Styrofoam insulation (which has an aluminum vapor barrier on both sides) from a local lumber yard. Other materials you might need are masking tape for temporary fastening while you are working to get a good fit and some good duct tape for the final assembly of the slabs of Styrofoam. Some people have tried glue, but I don't think it works well and certainly isn't handy like the tape.

Cut the pieces obviously oversized as you work. It is easy to quickly trim them for a better fit as you go. I used a small hand saw, an old serrated steak knife, a wood rasp, a large pocket knife and some really coarse sandpaper. You will want a short measuring tape, too.

Begin with the piece next to the bottom of the glider--it will be relatively small. Make it fit the seat pan well in order to help keep the finished cushion from sliding out of place. Add another piece above (which will be larger). Make it fit the shape of the glider around its edges using the wood rasp. Tape the two together. Add another layer as before. After the first small slab, you will need to make the sides taper wider at the forward end. I left them narrower than the space available by about 2-3 inches on each side and use that space for small items which I might carry during a flight. I also left a space at the lower-rear where our roll-up tool pouch rests.

Depending on your size and desired seating position, you will want to extend the second or third (perhaps fourth) slab so that it goes past the stick on each side. Then, all the higher layers also continue forward and probably will also need some tapered pieces in between them to build up for support of your thighs. You can score or notch the foam where needed to make it fit over the bend in the seat/floorboards. The parts of the cushion under my legs are the thickest of all.

During construction, after the first couple of layers of foam, get in the glider and check what is needed in the way of additional height and shape. Don't hesitate to use partial and tapered pieces of foam--just tape them together and try the cushion on for size as it grows! The wood rasp makes for quick work when fitting to the seat pan and to your seat. If you don't like something, it is easy to throw it away and try again!

A cushion which is springy and soft may feel good when you initially sit on it, but it will not support your weight well and will tend to cut off your circulation. Multiple cushions tend to move around and leave you in the wrong position. What you want is a dense cushion that when completed puts you in the right position up-down and also forward-back and has the correct tilt for comfort. Your weight should be spread as evenly as possible over the cushion, from just behind your knees to slightly above the end of your spine. Don't overlook side to side weight distribution; sculpture the shape of the top layer of Styrofoam to fit you. Save a little bit of space at the top for a thin layer of upholstery foam (as dense as possible) to take up the slack spots and provide a bit of softness. I used a piece 1/2" thick.

Get yours all put together with tape and then fly with it. Readjust if needed. When you are satisfied with the fit, tape it up well with the duct tape. Then cover it with a strong cotton cloth such as denim. This will require some hand sewing. We built ours this way about 18 years ago, and it is still in use. Later, I made a similar seat back cushion which is much less complicated. It fits flat against the plywood seat back and is curved in front to fit me. Wider at the top, narrow at the base. It is only used when we're not wearing a parachute.

The amount of time needed for construction of your custom cushion might be less than the time you would otherwise be miserable during a Silver Duration flight!