Nah, 245-50s when they wear out we'll look into widing the JZA70 rims and throwing something from 255-275 back there.
Whats funny is that Fs=FnXu.
That is force of static friction is equal to the force excerted on the tire from the ground times the coefficient of friction between the tire and the ground.
Basically, the width of the tire has nothing to do with its ability to grip the road. So dynamically, the only thing width does is give the sidewall added strength, which helps the footprint flex and stay planted on the ground.
My Point?
What ever size tire goes back there will be FAT and TALL.