Record Clamp for Rega P5?

I would be very cautious about using a very heavy weight as opposed to a clamp on a Rega turntable.

I use a clamp that holds the record down by clamping on to the spindle.

The Rega tables have very very low torque motors and I'm not sure how long they would stand up to having several extra pounds to spin around. At the very least, if you're going to use something heavy, you should start the platter spinning with your hand before you switch on the motor so that the motor doesn't die trying to start that hefty weight spinning.

I use a Clearaudio clamp on my P3 and it clamps the short spindle just fine.

Despite Rega believing that clamps don't make it sound better, I much prefer my P3 with clamp in place.