UL Inflatable Pad?

I'm 6'6" with very wide shoulders (think Rugby player). I love my ENO double wide but have struggled to find a bottom side solution that is wide enough that isn't too heavy. So here'e is my bright idea----

I'm gonna buy two Space blankets 56x84 6oz total
http://www.rei.com/product/407104/sp...rgency-blanket

I'm gonna bond them together with contact cement and duct tape and make a giant Mylar balloon. I'll leave a hole for a small rubber hose for inflation/deflation and add an oral inflation valve

http://www.ehow.com/how_6784663_make...c-balloon.html
http://www.ehow.com/how_5592989_bond-mylar.html
http://www.scubagoo.com/o-rings-regu...ion-valve.html

If it holds air and I think it will (cause Mylar balloons hold air forever!), I'll buy Silnylon and make a cover to go over my balloon. Add some shock cord and I've got a man sized inflatable UL underpad.

Weight-
Mylar 6 oz
Silnylon 5.5
Valve and little rubber hose 2 oz (guess)
Shock cord 1 oz guess
Glue and thread .5 oz guess

I reckon I'll be under a pound

Cost
Mylar 10
Silnylon 25
Valve 10
Shock cord 5
Glue 5

Maybe $60 bucks
WHAT DO YOU THINK? How warm would it be.. I'm looking for 40degrees
I don't want to try it if it won't work....

Underquilt...?

At 48"'s they are too narrow... Suit jacket 54XXL

Well,
A space blanket based UQ isn't exactly new. I think there are a few folks on here that have made something with fiber batting but using just air is a new concept. This should work as an excellent vapor barrier so condensation might be a problem depending on the temps and ventilation.

Unfortunately, even with the airspace I'm not sure how efficient the insulation will be. It's not just the air gap that creates a barrier to thermal transfer. You really need to encapsulate the air in very small pockets to prevent convection as much as possible. Down/synthetic insulation both create loft by holding the shell/lining apart but that loft also traps millions of little air pockets inside. This is why the latest trend of inflatable ground pads for cold weather still have some insulation inside (down air mat, BA Insulated Air Core, etc).

Regardless of the insulating qualities I'd be leery of the construction. One tiny pinhole turns your UQ into just a pair of space blankets. I guess if you're willing to stay awake and pump air into it all night that might not be a problem. As you huff and puff though you'll be pumping plenty of moisture inside that will condense and cause even more problems.

For the same money I think you could use one space blanket and a surplus poncho based or chopped down sleeping bag UQ. Weight would be a penalty but it would be a lot more reliable.

Good luck and take lots of pics.....

Hmmmm. why does my neo air work so well ?.. If I could only stay on it. I am looking into other bladders. gotta find just the right thickness