I have 4 duelers.. Next time i get tires, (i will have a new rear bumper , and a place to put the spare to be seen, I will get 5. The lsd sucks as it is. I wouldn't worry about 10 or 20 miles on the rear with different tires.. Just imagine the freeways in most urban areas.. they arn't straight as an arrow like in rural areas.. the LSD doesn't know if it is a long sweeping turn, or a different (minor) sized tire.. 30 to 31 don't worry. 33 to 30.. worry..
The front will pull a little if the tires are different.. for a long haul off the trail, back to town I would put it up ftont..