I am considering same thing -> 11" in front, and leaving stock 9" in rear. I have one pair of 11" hiding around here somewhere.
My '2A has 11" at both ends, and it is easy to lock up the rear, even with 32" or 31" tires. . . I am wondering if the '3A would be more "balanced" by leaving weak brakes in rear, and putting stronger ones in front.
Hoover will be used offroad, and my experience with '2A is that 9" are too scary, especially if they get wet.