That's the idea.
FYI, I have one fairly heavy lens in barrel that's held on a lens board by a stepped bushing. A retaining ring holds the bushing to the board, the front of the bushing has male threads that go into the barrel's internal rear threads; these look like filter threads but are in fact baffles to control stray light. I had Steve Grimes make the bushing that way because a cup-shaped bushing that accepted the lens' mounting threads would have been very expensive 'cos the mounting threads are around three inches forward from the end. Taking that approach with your Rodagon-G will make for a simpler bushing.
This brings up another point I've had to remind SKGrimes about from time to time. The bushing should be threaded internally, the threads like filter threads. You'll get much less flare that way than with a smooth interior.
Three thoughts about y'r sketch. The shutter end should go as deep into the shutter as possible, I'm not sure the bushing should butt up against the shutter's face plate, and there's no reason to make the bushing's walls as thin as possible. Stronger is better, you want something that is up to being stepped on. Not that I've ever dropped any of mine and stepped on them, but I sooner or later will. I've been spoiled; the shutters I use for front mounting are #1s, don't have conical face plates like the #3.
To contradict myself, now that I'm fully aware that the #3's face plate gets in the way putting the shutter in front of the lens might make life easier for the machinist. You'll still want a stepped bushing, but the step will be at 90 degrees.
Oh, and by the way, if you use an experienced photographer's machinist such as skgrimes explain the problem and explain how you'd solve it, then ask the machinist to propose what it sees as the best solution. The Dau brothers sometimes come up with solutions that are much better than mine.
Last edited by Dan Fromm; 10-25-2012 at 12:19 PM. Click to view previous post history.