After making a couple of thicker IX inserts with nylon and grosgrain binding, I decided to try hemming the three layers of a thinner one. All I did was cut to size, fold the three edges together twice and tape temporarily with masking tape, then stitch. It worked well; the result is light and has a pleasing feel.
This 30"x52" IX Insert weighs 9.8 oz. It is faced on one side with the last of my red nylon, and on the other with WM Digital Camo of Unknown Origin (nylon).
I'm going to make an UQ sized 45"x52" and see what kind of performance I get from two layers of IX.
EDIT: Added pix of the 45X52 IX Insert... just add suspension, and it's an UQ, the last thing I'll accomplish in 2009! It weighs 9.6 oz, because the grey nylon is lighter than the red nylon.