here's another experiment.
1" x 1" x 3/16 steel angle. UHMW guide-paddles. 1/2" thick UHMW backer plates and grade-8 hardware.
channel-iron would work well with this set-up too. If you "step" the outside of the guide paddles, you can decrease the ground contact width by about 4", but you have to adjust the tire-guide area to leave more material for an additional inner bolt...if that makes any sense at all.