How do you do this? I want to figure out the numbers for the new swingweights of my PD+ and More Control after adding as much lead as I did. I made them both 339 g with a balance point of 10-11 points Head Light.

Measure the distance using cm from the butt cap to where you put the lead (mid-point); then apply the following formula (using grams for the lead weight): added_sw = (dist - 10)^2 * lead_weight / 1000 That's it.

Well I added it in two places... In the handle and at 3/9. Shouldn't the handle counter it and make the swingweight stay close to the same? Or what?

The weight in the handle doesn't count. If anything, it will ADD something, but really nothing to count. Please note taht there's NO WAY to lower the swingweight adding mass, no matter where you put it.

Assuming this formula is correct, it provides only an estimate of the additional swing weight. It is an estimate because small differences in mass placement can lead to fairly large differences in swing weight. The same goes for the location of the added mass. Probably most important, however, is that there is a good chance that the starting point of the modified racquet is not the same as the published specs, either from manufacturing tolerances, addition of an overgrip, etc. This formula may get you into the ballpark, but it's almost certainly not exact.

If you add the weight in the handle at exactly the 10 cm point, there is no increase in swingweight. Of course, that is very hard to do unless you used fishing weights inside the handle. Greg is right, this calculation is approximate, but it is the correct formula and is as close as you're going to get without a direct measurement technique. The USRSA website has a manual method of measuring it on their website. Babolat's RDC and Alpha's Accuswing machines can measure it directly.