I use a buzzstop with a Mustang bridge on my Jaguar and it's great, no rattles and it gives the guitar a little more sustain with they added down pressure on the bridge. It also prevents the strings popping out of the saddles (but that's a problem caused by the way I play which nobody else seems to have).
I have a pair of Seymour SJAG1s and they are vacuum potted not fully wax saturated which means they squeal easily with a bit of gain. I potted them using a double-boiler wax bath and the problem was solved. If the SJAG3s you have are also vacuum potted that would probably be your problem.
Fran don't you have a wiki somewhere from when you potted your Jaguar pickups?