With only an 8
foot span, I'd look at a motorized
roller rig and lower and raise like a
roller shade. 2 inch
pvc won't have much deflection over 8 feet.
No more torque than you would need could probably be had from modding one of those
hand held
electric screwdrivers.
I have some nice stretch
cyc material on a 36
foot roller, and it's just rigged with a thin pull
line to bring it down and a rope wrap to take it back up.
No mechanical advantage or pulleys, and even that doesn't take much to move the 36
foot version with 14 feet of travel.
We find that when we use what I
call "roman shade" drops, your
drop lines generally have to be run through loops on the back of the cloth in order to control the fabric fold or accordion as it is taken up. Would look like heck on a
translucent drop.