LocostUSA.com

Wheelchair Gel Cushions......
my dad was ill a couple of years ago and needed additional padding on his backside during that time... I found Gel Pads at a local medical supply...

http://www.improvelife.com/Sale/Gel-Cushions

these things do most of the job of a thick cushion where there is not enough room for conventional seating... it occurred to me that it might be a good solution for bottom cushions in a locost build.. they seem to dampen vibration and provide cushion for bony backsides where there is minimal clearance... this link is just an example... there are lots of places and brands...
hope someone finds this useful..
Thanks
Heiti

Cool idea. I'd imagine they'd hold up well too, being meant for way longer usage amounts than these cars see.