A couple years back, boat wax (marine use) was the hot ticket for keeping snow from sticking. I have dropped the skids out of several of my sleds for various reasons and use that time to wax the gee whiz out of the inside of the tunnel. Especially the nooks, crannies, crevices and around the fasteners where snow will stick and turn to ice. I also do several coats on the large flat top and sides of the tunnel to help the snow/air mix to travel smoothly. Whether it lasts for a full season or not is questionable, but I do know that I don't get the snow build up in the tunnel like I used to. After living in Idaho and plowing snow, we used to use PAM or other non-stick cooking sprays on our plows and shovels to keep snow from sticking and freezing. If a person was to swap out the nozzle and tube from a WD-40 can and put it on the cooking spray can, I believe you could shoot up through the windows, around the track, and in front of the track to lube it up before a good snow ride. This probably won't do justice to a good track/tunnel clearance, but for those of us that aren't swapping a track/drivers out or doing a D&R, it may help with little effort before each ride. Unload the sled out of the trailer, tip it up on it side, spray down the tunnel, set back up right and get ready to ride.
Personally I like the idea of UHMW in the tunnel, but am leary of any extra parts that close to such a large moving mass where you can injest rocks, ice chunks, and even sticks to break it loose.