single stage gear reduction

I don't like Z10 gears on a Speed 900.

The Graupner Speed 900 axle is 6mm.

Inside diameter of the teeth is Z*M-(M*2.5)

Amount of Teeth * Module -(module*2.5)

10*1-(1*2.5)=7.5mm

With the 5mm hole, the teeth have a foot of (7.5-5)/2=1.25mm
With the 6mm hole, it's even worse. (7.5-6)/2= 0.75mm

It doesn't get better if you have an original Johnson motor with the 1/4 axle. (7.5-6.35)/2=0.575mm

probably will go for the technobots z12 mod1 for the pinion. no drill motor would ever demand 30 amps or over would it? (except in exceptional circumstances)