like stated before, just go with the +3 because the power difference from a +4 is not that much more to where it's worth trenching your cases, etc... if your trail riding you'll be fine. the only practical use for the +4 would be for drag racing since you wanna get every little bit of power you can out of the motor. if your not dragging i wouldnt suggest it. also when you trench you have an increased risk of breaking/cracking your cases since it can get pretty thin sometimes depending on who you get to do the work.