Further exploration turned up a mount that should fit my current, too large, hole: https://breedlovemounts.com/NMO_Trunk_Mount.html

Resurrecting an old thread to see if there are more or better ideas. I need to mount a new antenna on a race car. The metal roof has no headliner and is open to access. I plan to use a 1/4 wave whip tuned for 450-470 MHz. The current hole in the roof of the car is about 1-1/8” or so. The previous ow...