(sigh) Now, I refer you to the picture I posted above.

You'll recognize the parts where I did just what you're talking about. My circle template is green, as well.
I have to say, you're spot on with the technique. It's exactly what I would do if I wasn't going to get 8 resin castings of what I need. Besides, Stop, Look and Listen is starting tomorrow and I cleaned up my bench for the quick change to N-scale. The build the trucks are going on doesn't get officially started until August, so, I'm not rushing. I am going to knock out three or four S,L&L models and get back to this one. No worries. Besides, I want to take a bunch of Reference Pictures this April at IRM. Trucks, Motors, all sorts of things. You know the bookstore out there is a treasure trove as well.
'sall good!
Cuhail


















