slot.its boxers are exactly the same size as a nc2 and they have a very good balance of rpms and torque.
i find the nc5 very good and controlable on our flour/rally track and the nc6 too "speedy" for our 4mts straight. on a non-floured track like my home track, the nc6 rules.
i use the boxers as a nc2 replacement quite frequently on our speed track, both on f1´s and dtm´s (eurocars). at 15v these guys dig out 31k rpm with better much brakes than the nc4 without gearing up.