odie, the 30mm to 1 inch insert is really well made. I bought the Vicmarc outboard tool rest and adapted it to my PM3520 and it has the insert. And while I know any interface is a potential source for vibration, I haven't noticed any. The insert is machined so well that there is a suction pop, when I pull out the tool rest post.
As to the stop bar, probably have to override it with a wedge, sometimes I get up close and personable with the lathe, as in "one with the lathe..." maybe even spiritual...
Here's pics of the adapter. Did you hear the pop?
View attachment 37546 View attachment 37547
Ps. just trying to help you spend your money