[Dafni]

I never owned a Novak HV, but I heard many stories about thermal problems with this setup. So I think it is wise to stick to the recomended gearing fro the manufacturer. (stock wheels assumed)
One or two teeth more on the pinion will not kill your motor, I guess. But keep an eye on the temps.

Here's a quick gearing guideline:

Smaller pinion has the same effect as bigger spur.
Smaller pinion (or bigger spur) gives you more reduction.
Bigger pinion (or smaller spur) gives you less reduction

(reduction = ratio from motor turns to wheel turns)

Less reduction means more top speed (rpm at wheel) and less torque.
More reduction means less top speed, but more torque (power at take-off, if you want to put it like that)

Hope this helps