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?
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.