This is a mashup of two other models I found on Thingiverse - https://www.thingiverse.com/thing:5704716 for the Magquad lock mount, and https://www.thingiverse.com/thing:4935721 for the Galaxy fold 3 case.
I have not yet tested this design, but the it's meant for the quadlock magring to go in the op...
The folks in 3d printing helped me out greatly with this, and I was able to mash this together today. I haven't printed or tested it yet, but it's designed to be used with the quad mag ring. I'm going to use some very thin and strong 3m adhesive tape I have to ensure it is secure to the phone, and use for a quadlock mount on the bike if it actually works.
Perhaps this niche case will be useful for someone else?
I have Fold4 and been looking for QuadLock cases, but am afraid device is too heavy to be mounted on something like bicycle or motorcycle. For mounting in cars, sure I can see it being used.
It is very secure with the 3m transfer tape (snapped on pretty good without it, but i want to make sure its solid) l, and honestly works much better than my previous magsafe setup (oh snap 3.0). Wireless charging works fantastic, doesn't interfere with pen (when there aren't any magnetic accessories attached), and surprisingly wireless power share works.
I'm comfortable putting it on my bike at this point; however, I am going to put a skin on the case -- I don't like the blue alone, and I'm not sure how well PLA alone holds up to a drop.
PLA is pretty brittle but rigid. So it won't easily let your phone out of the case, but should it fall, I fully expect PLA to crack. PET-G is complete opposite. Elastic but strong.
Well, I'll let you know how it works once I actually make it.
I'm not that concerned about the case sticking to my phone, as long as the dimensions are right,. I have this very thin double-sided 3m adhesive (ACIT 3M 468 MP, Double-Sided Transfer, 5 Sheets (10'') https://a.co/d/4F0DrF3) - it's essentially the same thing that is in random consumer product made to stick to walls, phones, etc. I actually have it holding my current magsafe adapter to my phone (I moved it from a different case) and it's pretty solid.
Now-- my fingers are crossed that it holds to the mount well AND the mag ring works and charges well.