OmniFlect, Foylon, white poly, or Ultra Mylar?

Was going to buy a homebox but my space just isn't big enough, I'd have to cut the polls to shrink the thing by about 8"...

So instead I'm gonna make my own. But which material to use?

Foylon
OmniFlect
Sun Ultra Mylar
White Poly

My setup is in an attic so winter temps will be down to the low 40s or high 30s (fahrenheit) at night. I will probably use something like Reflectix as a back layer for insulation.

your temps are too cold at night, will need a heater.

You can leave your attic access open to allow heat in there,maybe even use a small fan.I'm doing a closet grow and I keep the door cracked.The light keeps it warm and a fan pulls in cool air from the unused room which is always cold to control the temp.Holds at a nice steady 75-80 (has spiked to 90 one day cause it was a fairly warm day)

Mylar is supposed to be 95-98% reflective so I think it's supposed to be the best but it's kinda flimsy.Gotta get the 2mil at least.Omniflect is more rigid/durable and is still 95% reflective and says it's real easy to clean so I'd go with that just for ease of use.

I'm bout to order some right now.I actually found this thread trying to find more info but after reading up I kinda answered my own question lol.

**The Cleardome solareflex stuff seems to be the best stuff (97.5%) and NASA uses it but looks like it's real expensive. http://home.att.net/~cleardomesolar/solarflex.html **