Steve,

I would also consider making a 3D printed motor mounting chassis with a full bottom plane with no chassis/lower hull mounting holes that would allow a buyer to make his own....a "GENERIC" that lets the buyer drill the holes and add bottom spacers for proper mounting...... Its a thought.....

If you can supply the outer diameter of the drive sprockets (assuming the right had drive or bevel gears are 1:1, a scale speed could be determined......

Springman