ok here it is!

[fin]

And if the tarp is the roof of the sock, how do you control condensation?

[heescha]

where you can see a "slit" in the sock...i'd have a waterproof zipper so you could open it up from "under" the tarp (where the tarp and sock are sewed together) and zip down all the way underneath or even back around again)

as for ventalation (once again this is where not being able to draw something out sucks)

the ventalation would be made the same way a tent rain fly vents...havning mesh with a "hood" over it. kinda like the picture at the bottom.

the way they keep the extra flap of fabric open is a super lightweight peice of plastic (kind like a thick zip tie) and there would be 2 vents on each side of the sock...both where the tarp and sock are sewn together...but underneath the tarp so no water could run in.