You can add as much weight as you want. Knowing that each cube weighs ~5 grams, just lay them out on top of the handle before anything, to see how far up you need to remove the foam in the handle and approximate your weight and balance.
I might remove some weight, definitely won't add any more. But, since I don't like the polarized feel, the more the weight is distributed further into the handle, the better.
I've played around ~2 hours with this set-up and it is uber-comfy. I've gotten positive remarks on the feel of the frame from others, the balance and weight. It does not come around like a 12.6oz racquet and the swing weight is more than manageable at this balance.