So... any ideas what the exact frame material specs are. 30mm O.D. per my calipers... do we know wall thickness and type of steel used? I need to section a piece out and weld in some replacement on my custom project.

mike

If you check the very rear of the frame you will notice the section for the tail light and rear fender connects to a piece that fits right into the frame. Measure that and you should have a clear idea of what to buy.
I've never cut one to check but I'd be reasonably sure the frames a neat fit back there

I checked my tail section today. The insert is 25mm and the Frame 30mm, so that just leaves the wall thickness at 2.5mm
If you are going to cut and shut the frame. Drill three holes around the tube an inch back from the end. When you insert the inner tube it will pass these three holes. Whilst still in the Jig and all squared up, weld up the holes on each piece of frame. That will keep things straight for when you do the full weld job.