I took Bumbi's case and copied it in TinkerCAD and then took some more copies which I then stretched and cropped it to add more of a top lip for better retention. I added a cross member across the bottom of the case for better rigidity and retention. Also increased the x-y size by 1% and Z by 5%. That all seems to make the case stay on better and protect the face.

I put a hole in the back to help with heat management. I think phone's lives and specifically the battery life is hurt because the phones get hot during use and charging.

Converted in Prusa with basically a slow PETG setting when I print with Taulman PCTPE. A few strings, but not bad. Printed on smooth bed on Prusa Mini with glue stick for adhesion and release.