This radius gauge is usefull when adjacent surfaces have different angle. 

It is made for a guide bearing 12.7mm or less. 

There is a 3 degrees lead in and lead out on the radius to avoid undercutting the adjacent surfaces.

The guide for the bottom plate have to be glued in place.

I joined 2 sets of .stl (25 and 50mm) but the radius can easily be modified in the attached Freecad file. Just select the proper sketch and modify the diameter of the circle as shown in the picture attached.

In my case, I trimmed the 2 adjacent edges first using a straight edge than apply a double sided tape to hold the gauge in place. 

I lay a 6mm piece of plywood behind the gauge to ensure the router base sits flat on the surface. 

I found the double sided tape can be reuse on 3-4 corners 

I have used PETG-HF