Some thoughts on the design: having the block of unthreaded holes on the shaft end reduces clearance on the actual business end of the unit. If using vertically, for steering for example, only get a couple of millimetres of clearance with the wheels that typically come with the TT motors and they are considerably larger than any on the wheels in the essentials set, also leaves no attachment points on the vertical-orientation top face. If the unthreaded holes were moved to the other end then there would be more vertical wheel clearance and they could be used as a pivot to use the motor bracket as a swing arm with suspension. Great work on Stemfie, having a lot of fun printing it and building the projects, cheers!

Thank you, @carl.olsson, for your great feedback! :) I have noted that and will implement it in future releases. I'm glad to hear that you are having fun with STEMFIE. :) You can download the power-transmission hubs for TT Motors below. - https://makerworld.com/en/models/439787 - https://makerworld.com/en/models/439754