Robust universal iPad stand

This will allow an ipad with case that has a thickness up to about 21mm wide. I think the original is designed just for the ipad. This remix allows for a case.

I should note - Cura complained that the part had gaps in the model in the uprights but was happy to slice and print without an issue. I was going to fix it but figured that, as it was printing correctly, there was probably no real need.