564, the amount of weight for beaver depends on the type of bottom.A hard or solid bottom takes more weight than a mucky or muddy bottom.Best bet is to haul some empty sacks with and fill with rocks and such at the site.Experiment a bit with your weights--a big beaver on a solid bottom takes a good heavy weight.
Your pvc should do alright with rats--also invest in a safety gripper,helps keep your hands --trap free. Tom