Update on my trip (albeit a bit over-do). The short story is there was no problem finding gas the entire 6100 mile loop. Ran low (~25 to empty) a couple times before re-fill but we were +75 mph for a large part of the trip.

Longer version, I carried a 1.75 rotopax gas container but didn't need it. The route was from NJ to the upper peninsula, across the northern states to Yellowstone, west to ID and south to UT. Then Million $ Hwy and back east to NJ across the middle states. (Did the southern states to NM in 19 on 2 wheels). I prefer the Triumph Trophy SE over the Spyder RT for long-haul comfort and range but the RT is a great all-around tourer.