I have done more than rub in the rear. While pounding though deep silt the rear kicked up HARD and hammered the wheel well into the rear door and completely sheared off the plastic "bolts" that hold on the rear grey trim in the process.

I think this was due more to the offset of the wheels moreso than the tire size. (32's)

While removal of the trim added some space, I still am debating if not using the BS extentions is a good idea especially with a longer travel spring pack.

There are allways tradeoffs.

Then again for your purposes you don't really care about finding the limits of your bump travel. I would use the BS extensions anyways as a precaution since you don't need the travel anyways.