@memtb thanks for the suggestion...I think I've seen those wide ones but after 10 minutes of searching online the only picture I've found was this:
pinterest . ca/pin/314900198915333079
Checked some retailers, tried "rv wide roller", "camper roller" and a few other search terms. In any case, I'm pretty sure I know what you are referring to. They are *much* wider than simple wheels, which, as you point out, can end up in a hole. Two wide rollers on either side would seem to be better. Have to think that one over...my initial thinking is that I'll start with these because I have them and keep the roller idea in my back pocket if it looks like I could use them.
Edit: found this thread. Some folks there are adamant that rollers and wheels should not be used and instead recommend skid plates. A dealer chimed in saying he replaces "dozens" of rear-quarter panels yearly because of rollers:
airforums. com/forums/f477/bumper-rollers-26660.html
Has me think that my intuition of preventing the rear from touching at all was on target (to the best of my abilities). It also has me think of going even more slowly over angle changes than I already have been. In my case, the wheels are attached to the frame so I think I have less risk than the airstream trailers might have. Still.
@opnspaces when underneath yesterday, I was looking at the rollers and thinking the same thing: the bottom of the roller might *just* protect the hitch receiver with the spacer removed. I'll measure it next time.
I took this picture hoping to show the angle...it's close:
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In the least, I can replace the spacer with a smaller one. Two extra inches!
At least I now know after my under-carriage investigations that the scraping sound I was hearing was actually the wheels. Phew.
@pianotuna it's very possible he means 3 feet...the roller I saw went clear across the rear bumper. Wish I could find a picture to post.
@DrewE good point. I can test before investing in the compressor.