I spent a few days reading up on wood lathe chisels and didn't really find much information on how to handle heavy internal interrupted cuts. Plus with the whole arrangement not being too rigid to begin with it seemed kinda dodgy.
So I thought i'd try something different.
It's a wooden arrangement built similar to a metal lathe cross-slide. Alot of the details in this cad are missing since i'm probably going to figure that stuff out in person.
Parts rough cut and arranged.
Used wood glue to attach the paper templates (I was going to mark it out properly but somehow all 3 of my tape measures have gone missing), and it was tough to get off with a chisel. So I tried just sanding it.
And... oh... looking at this photo, i've glued these parts on upside down. Hope that glue is still soft so I can separate them.