Sota reflex clamp problems

I recently sent my reflex camp back to Sota for repair. They rebuilt it , I was then able to pick up my 10 lb platter with just the clamp whereas before I could not. After 2 wks of use the clamp tension appeared to be less than after repair. I had to remove my platter this weekend and when I tried to lift it with just the clamp as Sota claims you can do , the clamp slipped. No damage to platter as I caught it w/my hands.
Has any body found this clamp to be less than satisfactory/had similar problems?
Are there other clamps that can be used on Sota tables that clearly work better?
I am not interested in upgrading to vacuum system.
thx,
jim