I like the machined approach. I dabble a bit into high power rocketry and made a jig from plexiglass.
Most of mine have carbon fiber fins fused into the tube so they have to be perfectly alligned.
I might borrow your idea if thats ok, it seems more accurate for the job.
-B-
I am curious on seeing some finished rockets if you have time to post them.
My last sucessful flight went just over a mile according to the GPS, the second flight I lost the chutte and came down hard and was a total loss. (GPS, ejection timer, camera, etc...)