cant you just buy a gas bottle & avoid the rental fee's? Thats what I did, I've got a pony bottle (50cf?? I think)like a small scuba tank size & every once in a while I have to go & swap it for a full tank. In the long run its probably much cheaper then renting a tank.

Even a big piece of plywood or cardboard blocking the wind from your weld area will do the trick.