Adding Weight to the Handle
Probably the easiest change you can make to your frame, is to add weight to your handle.
By adding a little weight at the tennis racquet handle you might just find the extra help you need to put that devastating touch on your volleys. Best of all, there will be little change in swing weight or maneuverability.
If this does not provide enough weight then you can wrap a 1 pence coin with bluetack and fit the coin flat into the space beneath the butt cap.
Once you find the extra weight you like, then substitute the bluetack with silicone. This will also help dampen vibrations.