Frank, the lip you describe runs the complete circle around the Chainglider chainring cover, and is flexible enough to part of the chainring and to glide over the thinner ends of spider spokes. It is therefore theoretically possible to centre the Chainglider for 38T chainrings over a 36T chainring, as Hebie claims. But it would be a satisfactory solution only if you never rode, pushed or otherwise disturbed your bike. Under any dynamic condition, sooner or later teeth would show whole, as on your bike.
You can certainly center the chainglider on a 36T chainring WITHOUT a chain mounted. WITH a chain mounted, the chain will hold the chainglider snug against the front of the chainring because of the lip. This wasn't obvious to me either at first. It took me a while of tugging and pushing with the chainglider half-installed to figure out why I couldn't push it forwards, until I noticed the lip.
Don't you have a bike with cheaper transmission you can try that on? Just asking... I think it possible that the lip will rub off most of the dirt the oil the exposed teeth pick up. So you may be right, the Chainglider may still offer a good measure of protection, and a Surly chainring is in any event virtually indestructible. I was thinking more of the expensive, and sometimes difficult to get off, Rohloff sprocket.
No, just one bike. I live in motels now and my storage bin is too small to comfortably store a spare bike, so I sold my old derailleur MTB and with it the cassette removal tool. I had some fond feelings for the former but good riddance to the latter!
Anyway, my whole bike was filthy for most of my three tours so far. For the Lassen tour, the chain was making horrible squeaking noises, it was so filthy, until I got to town and had a chance to clean it with some sort of spray stuff from the discount store. Despite all this dirt, the Rohloff sprocket shows little wear after 5000 miles. I think the secret is that I change the chain after each tour, which is never more than 3000 miles and I soak the chain liberally with lubricant (white lightening epic ride silicone lube) while on tour. My chain has never exceeeded the .75% mark on the chain wear gauge after a tour.
I believe those horribly worn sprockets you sometimes see are due to people running a very worn chain, and they do this with Rohloff systems because they can, not because it is such a great idea. It goes against the old derailleur wisdom which was to replace chains frequently so as to avoid changing chainrings and cassettes. Andy Blance apparently runs his chain into the ground, but he also notes that using a succession of cheap chains is also possible. And SRAM PC830 chains ARE cheap here in the United States. I get mine for under $10, including tax and shipping, and I could get them for $8 if I ordered in bulk. So that's $30/year if I take 3 tours, or about £20/year. Aside from sparing the sprocket and chainring, I think frequently replacing the chain is good simply because the chain has more moving parts than the rest of the bike combined and is subjected to a lot of wear and tear even if kept immaculately clean and well-lubricated. Frequent replacement means less likelihood of the chain breaking in the field. Not that I've had this happen to me, and of course I carry some spare links and spare master links just for this contingency.
My main concern about this chainglider was the potential for rubbing the Rohloff hub shell, but that problems seems completely fixed with the current version. As is, the chainglider will protect me from most filth on the chain and that alone probably justifies the weight (250g), since I was already considering getting the Thorn chain guard for this purpose, which supposedly weighs 135g (and also requires changing the bottom bracket, which is a PITA), but that would only have protected me from part of the filth. I keep my pants secured against my legs with velcro straps I sewed to the pants, but I sometime find myself leaning the chain against my leg while stopped and fiddling with the GPS or items in my handlebar bag, and the Hebie will protect against soiling when that happens. So for 115g more than the Thorn chain guard, I get much better protection from dirt. If the Hebie also allows me to dispense with my toothbrush and bottle of chain cleaning fluid (20g + 140g = 160g) by reducing if not eliminating chain filth, then it is a net reduction in weight.