Sweet deal, and I've been tempted myself. My buddy has one, and I've shot it with both slugs and 3.5" turkey loads.
All I can say is (and I'm halfway serious) check with your orthopedic surgeon to make sure you're sturdy and healthy enough to take the 70 ft-lbs of recoil those things will generate.
Forget the 3.5" mags. Stick with 3". That's plenty for turkey.