I've used Nigel's motors in tramcars and I am also designing one into a saddle tank of my own. I use Nigel's belt drive which gives a reduction of 3.6 : 1 in a single stage; impossible with gears in the same space. I then use the 14 : 1 Tenshodo worm gear set for an overall reduction of ~ 50 : 1. The belt drive is quite quiet whereas spur gears at the higher speed, before the worm, can be noisy. I had to use the Tenshodo gears because the tram wheels are only 5.25mm dia. but I may use a larger gearset in the saddle tank.
Regards Roger