Rega P7 + Dynavector DV20X HO

I recently upgraded my P5/Exact combo to a P7/DV20X. The DV cartridge was so heavy that I had to use the stock wt moved to then end of the stub to get the arm to almost balance. With wt at end of stub it allowed a VTF of 1.9g with dial set to zero. I am thinking of adding an aftermarket wt to the mix so I can use the actual VTF gauge and set my VTF to 1.7g. Any recommendations for weight to use.
Maybe you can add weight to the one you already have? I'm pondering doing the same. With a 20XL on my RB300 the counterweight is all the way back. I'm wondering if a heavier one closer to the pivot would be better.

If I ever find time, I might drill and tap some holes on the sides of the weight. That way I can bolt some brass or something right to it. Seems to me it is best to spread the mass to the sides, thus increasing lateral dynamic inertia without affecting the vertical.

I have decided to get the Rega heavy weight - a larger version of the tungsten weight. It is best to have the counter weight closer to the pivot point.

You seem to have a good idea - be very careful on your tapping holes on the side. They will need to be exactly 180° opposite of each other or you may induce some skating into the tonearm.