I have a clamp from, Mitchell (I think) that's made for Regas and it's a spindle grabber...on a Linn...works great and will keep the record on there in a strong windstorm. Seriously, you don't want your vinyl to blow off the table although I suppose you could simply close the window.
Turntable weight affects speed
I tried a Thorens tt weight on my Thorens TD-850 belt-drive tt. It noticeably slowed it down. It seems like extra weight on the bearing would affect any tt, but what do I know? Is a speed control (and strobe/test pattern) generally required to use a turntable weight while maintaining the proper speed?