For now, I'm aiming for the design to use the more common SG90 or MG90S servo motors. These servos are fairly popular for their small size and affordability, and can be purchased for a few dollars each. Unfortunately, with the popularity of these servos, many manufactures create similar looking servo motors under the same naming but with subtle differences in how they're made. Some SG90/MG90S servos have different casing, horn height, horn dimensions, potentiometer construction and some even used a digital control system instead of an analogue system. Adapting the design to suite all different variations would be quite difficult but they still at least maintain roughly the similar dimensions of around 12x23mm.

For servo case gear height from mounting, the variation between same models can vary quite drastically between vendors (or even same vendors). Horn height also has slight differences which adds to things to work around.