Bman
Changing your advance springs or changing the mass of the wieghts will affect your ignition timing advance curve. what effect this has on your engine will depend on to many factors to mention. What works for one engine combo may be bad for another.
Putting lighter springs in will increase the rate of advance, heavier springs will slow down the advance. Adding wieght will increase the rate where as lighter wieghts slow it down. What is good for your engine? I couldn't tell you, you'll have to experiment to find out.
There are tuning kits availible that let you change springs to adjust your advance. I suggest you get one and play with it until you find what works best for you.
Good luck
Clark