Cartridge too heavy for tonearm counterweight...

I had a similar amazing experience with the the F-2 Titanium Heavyweight Counterweight sold by Gregory_Kerry, a member of Audiogon. You can contact him through the internal Audiogon member email contact system. I put it on my humble Rega RB-300.
This single upgrade astounded all listeners with the enhanced solidity, bass weight, and bass extension, along with clarity, harmonic richness, and musicality (overused word, but really appropriate here) over the entire audible range. You can tell I'm a fan. A great item at a fair price is deserving of praise.
It seemed to mate beautifully with my Non-felt record mat, although someday I have to see if Herbie's turntable mat is a further upgrade, as its website promises.
It is a great idea for all of us budget-minded, vinyl loving audiophiles. The current price is around $130, and well worth it.

When you buy a counterweight for an OL arm or an OL modded Rega arm, you must specify that it is an OL end-stub on the arm. Otherwise, you already know what happens.

If you must add weight to the counterweight, add it at the bottom. This will help the tracking and the sound.

Try bubble gum. Sweet midrange.

Use 2 sided carpet tape to adhere a round washer around the center hole. Both sides if needed.