After reading all these and rethinking, I have something to add.
The 275/45/18 M&Hs I have are on 18x9" rims. Which, at street use tire pressures, crown quite a bit. 20psi at the track, they are golden. I've tried them from 32 down to 25 on the street, and they still crown out. (at 25psi, the sidewalls feel awful spongy, which makes them weird to drive in traffic....)
I think if I had a 10" rim with those tires, they would do much better in the rain. Think maybe they would run truer to "flat" across the entire tread pattern.