Are you sure you don't just need to readjust your math?
The TW Professor didn't add 100 g to a frame that weighed 0. It was 100 g plus whatever the hitting weight (effective mass at a particular point) of the particular racket used in the test. So, the magic number isn't 100 at 3&9; it's whatever the final total hitting weight of the racket was at 3&9 after the 100 g was added.
Instead of trying to find a frame with a SW of 260 so that you can add the 60 g that you have your mind set on, maybe you need to calculate the ideal hitting weight that you are trying to achieve at 3&9. Then, once you know your ideal hitting weight in that location, you can use the hitting weight numbers that the TW Professor has already compiled to find frames that can let you reach your goal with a different amount of added lead.
For example, you might find a frame with a SW of 300 that does exactly what you want when you add 30 g at 3&9 without pushing you out of your comfort zone in terms of overall specs. Or, you might find a frame with an even higher swingweight that works with only 15 g added.
This might make it easier to find a platform to get started on.
Before you attempt to beat the odds, be sure you can survive the odds beating you.