bigger rear disc in rear than front a problem I assume?

My Thoughts..............

If the co-efficient of friction is greater in the rear than the front, the rears may lock up before the front and you'll spin out. I am not sure what your situation would be with the combo you are suggesting, but it would make sense to me, that an adjustable proportioning valve may allow you to dial down the rear breaks to avoid this. Just my 2c:)