Here's more info on using the tarp. The frame of the run is metal tubing, and the pieces are 4' apart, so there's not a lot of load bearing strength there. I put chicken wire over the roof to help support the tarp, so it wouldn't sag with the snow load. I also broomed the snow off every time it snuisance now an inch or more. That took about 3 minutes, so not a big deal. Our snow can be very wet and heavy.
Pull the tarp snug to help keep it from sagging, as chicken wire isn't very strong either. Also, you want to keep it from flapping in the wind.
Dang, I really do want to build a pallet sh.ngle roof now.