Originally Posted by travlerajm
Correct - the formulas do not need to be adjusted when you go to a longer racquet, and you can use approximately the same target specs. But keep in mind that while the swing dynamics will stay the same, the impact dynamics will change with a longer racquet. That is, the effective mass at the hitting zone will be lower with longer racquet - so the feel and ball response of the impact will change. The longer racquet will be less solid and less powerful for the same groundstroke or volley stroke. But the added leverage may make it easier to produce spin and ball velocity on the serve.
Because of the lower hitting weight for a given mass, balance, and SW, you may find that you prefer a higher SW for the extended racquet. I would recommend keeping the MgR/I and MgR'/I' values the same, but bump the SW up a bit to compensate for the lower hitting weight, thereby preserving a similar level of mass in the racquet head.
Thanks for the advice! I've had much better luck settling on MgR/I than on weight/SW, so I'll keep this in mind if I go extended.
Also, to everyone else: for those of you who are skeptical of MgR/I, I'd highly recommend playing around with it if you aren't happy with your current racket setup. After a very long racket search, I settled on a Prestige MP, but it still didn't feel quite right. After stumbling on this thread, I realized that stock Prestiges have a much higher MgR/I than most other rackets. They started feeling better and better as I brought the MgR/I down until I finally found an ideal level (~21.15 - I'm 5'8", so I think the slightly higher than normal MgR/I makes sense). Then I started to think about all the rackets I'd demoed, and began calculating their stock MgR/I - most had MgR/I's around 20.8! The two with which I felt I had the best control, though - Bio 200 and TFight 325 - both had MgR/I's around 21.1. Certainly there were other factors at play here, and I don't completely understand the physics, but these two things together have convinced me that MgR/I is a valuable tool.