I’m almost done with my version of a 3D printable antenna guide. It consists of a pentagonal center, an end piece with curved ends to match the antenna base, and several spacers of 100, 200, and 300mm lengths. Everything can be printed on smaller machines like the Ender 3 Pro.
The minimum radius is 14cm, and max just depends on the spacers you print and use.
My intent is to put adhesive magnetic backing on the pieces so they will stay put, but not that you leave this on the roof at high speed. The pieces interlock, a bit like puzzle pieces so that they align easily, and they have alignment ridges for visual confirmation.
I will be publishing both finished STL files and OpenSCAD source so you can tweak things. Most notably the diameter of the end that fits the antenna base. Yours is likely different than mine. I could have done a “V” end, but then the radius would depend on the antenna base diameter.
Mail me at kc6ete at gmail if you would like to get pre-publication files, otherwise they should be published on yeggi by some time this weekend.