Still looking for something to replace the spur gear, so there is nothing to fit the axle in hobbyking. I think mixing 3D printed gears with metal one will destroy the metal.
For a lot of my rc stuff I’ve always been told to leave at least one gear plastic (generally production gears though) so there is a point for failure. Otherwise the next weekest thing will have to be the failure point. Not the advice I always follow, but thought I’d put it out there…