VPI 3D arm

I'm referring to Stringreen's comment.  It has always been purported that the 3d arm and the classic metal are interchangeable.   Not so without changing out the pivot piece which VPI is theoretically selling me should they decide to ship it.  Hope springs eternal. 

All well and good but nobody answered the OPS question. That is a thread hijack folks.

Sure they did,  Please re-read the first two responses.

@drewmb1 , I am using two different metal Classic arms in lew of the 3D arm that came on my Prime. One of the arms are off a Classic 1 and the other from a Classic 3 with no mods, these arms are interchangeable, I believe the problem is with some of the older 10 inch arms.

Yes, you are correct.  It's actually that the damping well interferes with the 3d arm.