My Boardy Mcboardface is very similar to your 2wd iteration of the racebro in terms of weight distribution (84 cell 21700 battery, pelican 1200, M1AT, 6485s, RTKP) so I think I can speak a bit to how the rear heavy weight distribution effects behavior in the air.
If you’re worried about how it’ll feel off-road doing jumps with substantially more weight in the rear, I don’t think it matters that much, in the air the rear end will generally just follow wherever you direct the front, IME it’s much more important to have the front end lightweight than anything else related to distribution. If you can use the front end to direct the board where you want it to go your momentum will generally work the rear end out to go where you want it to go.
There’s a lot of momentum behind your body when you’re doing jumps and it feels to me (my bodyweight fluctuates pretty heavily between about 75-85kg) like your momentum has enough influence over the board that as long as you don’t go off the jump funny everything else kinda just works itself out
Super keen to see how this build turns out!!!