I have a 8'x10' hoop house tractor that I raise my broilers in. It's covered with 'heavy duty' poly tarps that I bought at TSC. Unfortunately they only last 2 years before shredding due to UV, hot/cold, snow, etc. I've tried the silver/black and green/black models but both last about the same. Does anyone have a recommendation for a better cover? I've heard of old billboard signs, but they were very pricey.