The outer roll bar (Mk.3) sits in a curve in the bodywork. To get a flat escutcheon to fit, one would need to make it oval but I'm thinking about 3D printing escutcheons which won't necessarily flex that much.

I printed a jig to fit around the rollbar with 20 index notches around the outside. The jig sits horizontal on the rollbar and let me measure the drop down to the bodywork. I also drilled holes nearer to the centre so I could get a second set of readings.

Someone might find it useful...

https://www.thingiverse.com/thing:4547987