Not a problem after an axle flip. You will gain the thickness of the axles (3"), and the new spring perch ~1.5". I've done this on two 5ers and a TT. Our current 5er already has the axles below the spring, but I added a 1" spacer for more tire to wheel well clearance. Since doing that, pulled about 15,000 miles in 2 years. You will not be top heavy for that little amount of added height nor will it negatively change any handling characteristics but quite possibly will improve handling a bit by adjusting the weight over all four wheels instead of being a bit heavy on the rear axle and wearing those two tire faster (maybe?)
