My own experience is a substitution of the 12" 3D arm for an original on a very original 12" base. As I wrote above, I did need to change the original lower bearing for the "spike" now used. At its closest point (which is just after leaving the rest position) the larger azimuth side weight clears the tower by about 1/2 inch. While on the record the distance is far larger.
On the pictures of the arms at the VPI site though, the azimuth side weights of the 10" arms seem quite a bit smaller than those of the 12" arms.
So who knows, but best to figure it out before purchase.