"And no, a 5 gallon portable can isn’t a reasonable substitute for either of the above options."
You must have a hell of a bladder! A stop is a stop as far as I am concerned. No I don't care if I spend a few bucks more for a truck stop fill.
I do miss my 35 gallon tank, I know only 3 gallons less now but it makes a difference as I had specific stops along the West Coast. Used the 5 one time as I had not calculated in the long grade from the Columbia River to Yakima, WA.
Bottom line people need to do what works for them. I just think everyone should decide with real world experience before spending BIG $$$.