Kidde Smoke Detector Mounting Adapter, remix

While replacing my 10 year old Kiddie wired Smoke Detectors, I noticed that the new detectors were not compatible with the old mounts, and I could just relocate the detectors, but then I would have to patch and deal with the AC connection in junction box.

I found https://www.thingiverse.com/thing:1416038, but it looks like my inner ring fit exactly within the 1.5" hole in my old mount, so I needed to remove a little bit of the upper shape to fit.

After simply reducing the size of the up