When I was talking about forehand beta angles, I was referring to the angle between the forearm and the racquet, where the beta angle would change depend on the amount of wrist extension (being naturally extended, that is). I did not mean the angle that changes due to wrist ulnar/radial deviation, which is in the same plane of motion as shifting from a pistol to hammer grip in your hand.
In my mind (I hope I can explain this right), I’m seeing the beta angle being most relevant for forehands between the x and z axes, and the beta angle being most relevant for serves between the x and y axes. For everything below, I see the x axis as being horizontal and the y axis as being vertical.
On the serve, I can see an advantage of pronation with the hammer grip from what you are saying and from this video http://www.youtube.com/watch?v=1t6bLABbebc
since increasing the beta angle (angling the racquet from the y axis closer to the x axis) increases the opening of the cone (that you were talking about before), which is a visualization for increasing pronation’s range (or radius). Wrist radial deviation also, technically, increases that beta angle. The way I was taught to hit a flat serve (with pronation) intentionally has a small beta angle between the y and z axes (wrist is being flexed, only to hit higher or lower trajectory over the net, resulting in a shallower or deeper serve) and I’d say even less for the x and z axes (since you mostly turn the body to impart horizontal direction on a flat serve, not the racquet face), and when all the rust if off my shoulder I can hit +100mph. Now, as I’m trying to visualize this in a mall before work and without a racquet, I can see the x and z beta angle being more relevant on a second serve when trying to impart spin.
But if I think of a beta angle between the x and y axes for a forehand, I don’t see an advantage of using pronation, I see a disadvantage. I am imagining the arm outstretched and parallel to the ground. A high beta angle will angle the racquet from the x axis closer to the y axis, making the long axis of the racquet more perpendicular with your arm (and the ground). From this position, pronation results in a downward slapping motion like nothing seen on the pro tour haha. Now, if the beta angle was between the x and z axes, like all of the photos I posted and the Fish photo posted above (Im trying to find pictures of forehands at contact taken from overhead for even better examples), at contact the racquet will brush up on the ball, not pat/slap it down. The greater the beta angle, the more windshield wiper motion will occur and the greater pronation’s range (or radius) is. So the same rules about beta angle apply, I just think they are in different axes. Look at pictures of Nadal and Novak’s forehands at contact, the majority have the long axis of the racquet horizontal, so somehow they are compensating for the additional 30 degrees given by their hammer grips.
I will try to get some edited pictures with the axes on them later today to further illustrate.