I have a very early Prime 21 Plus (sign-off sheet says Nov 2020). I have to raise the VTA almost to the top to get the Shyla cartridge / gimbal tonearm level with the record surface. Unfortunately, the locking screw engages with the VTA tower thread, not the brass bushing. Not a huge deal, it sounds great, but I have noticed some pictures of VPI Prime 21's with what looks like a taller arm base (the black nylon ring the arm assembly sits on). Has the arm base been modified? Is it retrofittable? Thanks, Mike.