Maybe if works fine, but I'm never going to use that method. Pencils, phone books, stopwatches, not gonna do it.
Out of curiosity, and perhaps boredom, I conducted an extensive internet search to find a formula for racket swingweight. I found sites that had sw calculators for fly rods and golf clubs but not much for tennis rackets. The racket stringers association supposedly has a sw calculator but one has to be a member to use it.
I found one site, racquetscience, that has a simple formula that supposedly closely approximates racket swingweight. Devised by a guy named Avi Wiezel who is an engineering prof at Arizona State Univ. I cannot vouch for the formula's accuracy but maybe one of the resident sw geeks can.
SW (kg.cm^2) = 10 x racket length in cm + racket weight in grams
- 690 (constant?) +5 x balance points (+ number for head heavy points, - number for head light points)
Swing Weight:
Example: A 3 points Head Heavy racquet 70 cm long racquet weighting 265 g has a swing weight of 10*70 + 265 - 690 + 5 * 3 = 290.
How to remember the number 690? Think of it this way: a 69 cm long balanced racket of 300g has the swing weight 300 kg·cm²
According to our friend Avi, my 408 gram, 11 points head light, customized PT280 would have a sw as follows:
10 x 69 + 408 -690 + 5 x -11 =
690 + 408 -690 + -55 =
408 -55 = 353
Sound right?
If one is using 27 inch (68.58cm rounded to 69cm) frames, it seems to me you could lose a couple of terms in Avi's equation and it would come out the same; the 690's cancel and the formula simplifies down to racket weight in grams - 5 x balance points (+ for hh balance points, and - for hl balance points)
Edit: Having compared Dr Wiezel's simplified SW formula to some real world actuals, it seems his formula doesn't hold water.
Anyone here know for certain what factors influence SW? Length, balance, total weight, all yes. How about head size?
If anyone knows a better formula that works in practice, post away.