I'm probably gonna get booed off stage for this statement. But it seems to me like Novak has the best mid-size motor right now, the HV. Why not take advantage of all that sensor work they put into it. :D If you used the 7.5 (3000kv) then the bigger rotor, which is supposed to drop the kv, and figure that it is an unloaded rating, it should be fine on 6s.
I'm thinking of running this combo, in 4.5 flavor, on 4s, in the new Slash 4x4 .