RE: Tygon & Glow fuel
I located some nice Tygon at a local small engine shop. Comparable price to hobby stores (but my nearest LHS is 70 miles, this shop is much closer), pure brand stuff. With the idea in mind of multi-fuel use I did a few tests:
Immersed a short length in 25% nitro (1/2A glow) fuel. After about a week, the Tygon had shrunk to 2/3 original diameter or less, turned a darker yellow, more a deep amber, in color, and had the stiffness of unboiled pasta. (Not as brittle or breakable, but DEFINITELY not flexible.) I did allow it to dry after retrieving it from the glow fuel, to see if it would regain some of its characteristics - it didn't.
Silicone fuel tubing withstands the heat at a muffler tap. Tygon does not. It also quasi-melts, like fishtank airline tubing, in contact with fairly hot parts of a running engine.
I conclude that it is great stuff for kerosene, ether, castor, and most likely gasoline, and petroleum-based oils, but not for close passage to hot engine parts, or exposure to moderate/high nitro fuels. Used where appropriate, good stuff.