Just finished it this week. I think I got the idea from this site, but not sure. Built a 4x4 frame and hung stall mats from TSC. Put the whole thing on casters and now I have a fully mobile 6x8 foot backstop. I shoot a PSE that has been chronied at over 315fps with hunting arrows and this thing stopped them no prob. Field tips broad heads it doesn't care. probally got around a 120$ in it and could not be happier. I will post some pics later and thanks for the good ideas.