So far I am sensing that we're mainly leaning toward this not being a good idea.
Each to his own though ....50 profile tyres on 20's will last a few hrs on the potholes round here .... not to mention giving a hard ride .
thinking there shouldn't be windup if open diffs on the front and centre.
let us know how you get on SidI have 5mm overall height difference caused by new tyres on front, worn on rear, and it winds up when reversing really badly, yours will do the same.
I run rears at 40psi and fronts at 35psi to compensate, but even then its knocks if I reverse around a corner.
....looking at toyota specs, they did give an option for 285/50/20 from factory with ET25.....