We are currently building our run, 20x12, with 4x4s spaced 48in on center. The hardware cloth will be ran vertically down the 4x4s. We are doing welded wire for the roof, but eventually will put plastic roofing on. We are in NJ and get decent snow in the winter. Should I do 12 ft 2x4s across as roof supports between the 4x4s or something bigger like 2x6s? Only reason for not choosing something bigger than 2x4 would be that they will be significantly cheaper if I can get away with them. But I want to do it right and if 2x6 would be way better, I'll do them. Any suggestions?