Hi Oh Captain -
Just a few quick notes on 12:00, 3:00 & 9:00 locations that have been mentioned.
The free lunch at 3-9: Often you will arrive at nearly identical swingweights with adding either 3 grams at the tip, or 6 grams (3 on each side) at 3:00 and 9:00. If you look at this choice in a cost vs benefit sort of way, what you will find is:
1. You will pay just about the same price... ie, both racquets will be more difficult to swing, by about the same amount of increased difficulty
2. Both racquets will have the about the same potential power increase for most, but not all strokes.
3. But only one, the 3-9 location, adds lateral stability for shots hit just outside the sweet spot. It's almost as if you get a free lunch with the 3-9 location.
However, if you want to dig deeper, the choice becomes more nuanced. One big factor hardly ever discussed here is that every racquet ever made since the beginning of time has a dead spot. There is a spot near the tip of every frame where the ball simply does not want to bounce. You can confirm this yourself at home very easily. Just press the butt of the racquet onto the edge of a table, with the remainder of the frame hanging freely off the edge. If you drop a ball onto various locations on the string bed, what you will discover is that the ball bounces pretty high right in the center. It bounces even a little higher, slightly south of center. But out near the tip, the ball just not want to bounce at all. Complete dudsville.
About the tip/dead spot : The tip of the racquet is moving very quickly in a serving motion, fairly quickly when you are hitting a groundie, and not very quickly at all when you are blocking back a 100 mph serve. We have all noticed that you can hit the ball near the tip on a serve and still get a pretty decent result. (It hurts like hell but the ball still goes over the net with decent pace) That's because on a serve, the tip is traveling pretty fast (about 100 mph on a 100 mph serve) and is traveling faster than the speed of the strings on center. The added acceleration there cancels out some of the dead spot deficiency. You've also probably noticed when you strike the ball near the tip when you are blocking back a tough 1st serve, the ball often lands at the bottom of the net. The tip isn't moving fast enough to compensate for the dead spot.
(to be continued... gotta grab the train back to Jackville, and that's enough to chew on for now)
-Jack