I have been reading your posts on this subject for a while and I finally had to throw my 2 cents in....I know you guys have probably already tried these:
What about a piece of 3/4" heater hose stretched over the pipe and glued into place with jb weld or suitable epoxy? Would that just get torn up?
Or contour the pipe so that more of it contacts the tire? Or a combo of both?
If you have compressed air, my favorite tool (besides the welder and the cuttin' torch) is my 3" cutting wheel disc grinder. That can be used to cut a deep texture into the pipe in no time.
If you have a welder, perhaps run the engine and weld concentric circles around the pipe until it has a high spot on either side of the center track of the tire, then grind it to match the tread contour perfectly. The larger the contact area with the tread, the less contact pressure needed to grip it, translates to faster speeds and the longer everything will last.