STS-Pi - Roving Robot Kit
(PimCar_1) falls outside the support surface with the type of powerbank at my disposal. Clearly the powerbank you mount is smaller in size and consequently maintains the center of gravity inside the support surface. In my opinion the solution (PimCar_2_3_4_5) with a flat-shaped (*) slim powerbank would allow us to insert and remove it (for example if we need to remove the uSD card) from below the Raspberry PCB. A possible solution (but not the only one ) is schematically indicated in the attached PimCar photos - and would involve 4 longer screws and other 4 nuts to allow the fixing, as well as the Raspberry, also on the back side, of the flat powerbank. The two transverse( or longitudinal) brackets to support the power bank should replace the two circular clamps used for anchoring the cylindrical powerbank to the rear side of the car.
In any you are doing a great and useful job. Compliments
(*) It depends from the market availability