I have a new MILL! (yes that deserves all capital letters thank you very much) It is a Jet JVM-830F and while not as big as a larger mill like a Bridgeport for mitering tubes it will work perfectly. For the past 14 frames I have filed the miters by hand and have gotten pretty good at getting a snugfit. However this is a very time consuming process and ultimately is not as accurate as having a good hole saw with a solid machine to cut the miters. Right now I do not have a collection of high quality hole saws (or even good ones for that matter) so with my test cuts the result has been slightly less than desirable. That said the end result cleaned up extremely quickly and with the proper attachments the mill should be a godsend.
Oh, and I decided to scrap my last MTB frame unfinished as I wanted it to be single speed compatible and I had already brazed in the low mount dropouts. My new frame is using Paragons sweet sliding rear dropouts and is almost completed. I went with pretty much the same geometry as my previous attempt except with the sliding dropouts I will be able to adjust the rear stays from 420mm to a little over 440mm.