Record clamp

Highly unlikely that it would do any harm to the table. 
I tried about 10 different clamps a few years ago on my Technics SP10mkII. On that table, the clamps definitely were more impactful than the weights that didn't clamp, including some very pricey ones like the HRS. 
The Michelle light clamp is a good one that won't add much mass. The Sota Reflex clamp was my favorite overall; it weighs 7.8oz. Cheers,
Spencer

Kiseki Purple Heart-$3200 MSRP cart
Rega P3 $900. Is this a typo, and should be P8?

Did I read the OP's question correctly?

Save your money for a P8, and the best phono stage you can afford. You're not hearing the potential of the cartridge. I'm sure it's a considerable upgrade from what you originally had, but the P3 will never be able to show the PH in it's best light.

Current Kiseki user and former Rega owner.

Hopefully your purchase of the Kiseki wasn't influenced by a sales person. That's a serious table/cartridge cost/performance imbalance going on there. Shame on the sales rep if was.

I agree! That cartridge needs a much nicer table, ( I am also a current Rega & Kiseki owner and former dealer for both). The P3 is an excellent table, but that Purple Heart deserves better!

I use an Aluminati weight on my P25.  They used to sell them on here.