Snow blower belts:
I have had the opposite experience with thrower belts. I run a hopped up QA-42B with an 18hp Mag in a 782 and have run the last 5+ seasons on 1 belt....but it must be tight. A positive belt tension stop is a MUST to keep it from backing off and getting loose/HOT....that ruins belts fast.
QA-42, 450, QA-36, etc........they all pull hard when pushed to operate well.
Again: Hydro for infinite speed (and hyd. lift!!!!), LOTS OF HORSEPOWER!!!!, and then feed it until the Kohler really barks..........at that point you've done all you can do!!!!
(then again, maybe the belt success I enjoy is because I bought 2 belts the first time........only way to guarantee you won't need the spare is to buy the spare!!!!!)