Similar question. I’d like to go from 15 to 20 gms in my Phantom 7.

You can buy a kit, and change the weights yourself, but I would send it to the Custom Shop to be completed. Titleist can correct me if I am wrong, but I am quite certain the weights are set to the optimum performance for that putter based on their testing. It's your putter, and you can do what you wish, but I would look at a different putter before changing the weights if you are not happy with your performance.

I have a 33 X12 and took the 20 out and put 25 back in, love the way it feels!