This got me thinking about the plastic ramps I have. I only put one end of fairly light cars on them, but it would still leave a mark if one or both failed at a bad time. So I cut chunks of 2x4 that slipped nicely into the pockets on the bottom. Four of them have got to add a substantial amount to the load capacity, and I don't see a downside other than adding a couple of pounds to each ramp.