In the meanwhile, while the gray paint is drying overnight, i decided to do the rudder servo mount as well.
This was simple - bolt the Hitec HS-125MG thin servo to the Tamjets mount, roughen the back of the mount with an Xacto blade, and glue in with 30 min epoxy mixed with some Aero-Seal to make it thick so it wouldnt run.

I positioned the entire servo with mount in the fin, in order to get the correct location for the servo horn, and while the plane it on its side, put some lead weights on the servo body to keep it in place until the epoxy hardens.