The VPI is a threaded spindle. My JVC's is not. I therefor assume all JVC's are not. I own both a VPI Aries and a JVC TT-81. On the VPI is the Black Diamond Racing clamp. They by the way, are only threaded. On the JVC is the Monster Cable clamp which is the same clamp which is sold under different names one of which is the Sumiko. I think the best clamp for the non-threaded spindles are the SOTA reflex clamp. It was the best clamp I ever owned. It is like the Racing clamp in that it can be made to tighten just about as tight as possible. I would not play a record without the use of a clamp. I want my record 'held' against the surface of the platter and not waving up and down as it goes around. An no, records are not all flat. Actually, most are not. It you don't believe this, then just take the corner of one of your post-it notes and see how often you are able to slide a sheet of it under your so called 'flat' record. Disappointing to say the least.
Regards,