[travelin texans]

This is one of those topics that will never end.
Personally I would/have/will continue to just inflate to the placard or the sidewall if I've upgraded to a higher load range.
The process of weighing & trying to cipher percentages for proper inflation is too much headache for me. If the weights indicate inflate to 70 psi & max is 80 psi I seriously doubt you'll notice any difference towing it with the extra 10 lbs.
Most every rver will be at or very near the max GVWR of their rv after they've used it several times so inflation to max is the easiest simplest inflation & your set for the day you reach the max gross weight. Legally no one is allowed to ride in a towable while traveling so there's no one to complain if the ride is a bit harsh.