Hi Doug. The higher OL arms do have the added lateral mass in the large bearing housing, and that has alot to do with the better sound of the higher end arms.
Thanks for the compliment from you, and Mark Baker.
The new Silver II will not accept the HiFi mod. It has a totally different end cap arrangement, and already has some weight out there.
I don't know if I'd call it the "Swinging Silver Bullet" but if you make it, and want to call it that, then that's what it will be called.