I would think that it would be necessary to completely recalculate the load capabilities when switching over to bents from stick walls. With stick walls, the load would be fairly evenly spread out top to bottom with fairly equal plates both top and bottom, but in a bent there is so much more mass up high. It is not simply a matter of dead lift capacity.

I imagine the 500# capacity rating assumes a moment somewhere towards the middle of the wall, whereas in a bent the moment will be much closer to the top plate, and thereefor require greater effort(and therefor strain on the rig) to initiate the lift.

My gut reaction is to find a better solution.