You can measure and do some math but there's something to consider, the 5er will vertically pivot differently compared to the TT. It won't change as much with the pivot being over the axle compared to the height change at the bumper.
I'd just try it. Like you said, go during low traffic, take someone along to watch and just go slowly to see what happens.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10