I'd like to install Confor foam in my glider but I'm not sure why such small pieces are sold or how they're supposed to be fitted to a glider.

How do other pilots attach the Confor foam to their seat pans so that the cushions retain the shape of the seat pan instead of springing back out?
Are the 16x18" Confor foam cushions supposed to be sat on or put behind the back or both?
Wouldn't a fitted, tapered Confor foam cushion that runs from the back all the way to the thighs makes more sense?
I don't have much headroom so how much does Confor foam compress when sat on?