Can you provide some details on your NMO roof mounts? I don’t see many brave enough to drill holes in the roof and I want to. My ham antenna mount does not give a ground plane and pretty much sucks. I have the Rago NMO that looks like a ditch mount. I use non ground plane antenna but not good results.
I had a friend do it who installs equipment in emergency vehicles, but I watched and helped a little. Pretty basic really; measured, marked, and drilled the holes. Mounted the bases, screwed on antennas. We did add a bead of silicone around the base in addition to the supplied gaskets. Works great. We only needed to drop the rearmost portion of the headliner to gain access. I’d do it again without reservation.