Recently changed from a TM Superfast 2.0 10.5 loft, which i grew to hate with a passion, to a 910D2 10.5 loft w/ Project X 6.0 7C3. I don't get to play with many other golfers so I really have no other knowledgeable opinion on this. I have been driving the ball better than I have in a while in terms of keeping it in the fairway with about a 270-280 average which I am thrilled with. The thing is that my ball flight can some times be ridiculously high.
Does that mean I could be leaving some distance on the table or am I just getting greedy?
Depending upon how much spin you put on the ball, there are cases where the launch can be too high. The less spin you have on the ball, the more you can get away with a slightly higher launch. Ultimately, you are looking for that penetrating ball flight, which in terms of your launch angle, can be around 14-15*. Usually going higher then that, with too much spin, can cause a reduction in carry distance.
I would recommend stopping by any local Club Fitter to see if they can get an accurate launch angle.
I'm using a very close shaft that you have on your D2 right now. I have a TM RBZ Project X Black 6.0 @ 46". I haven't gamed it enough to evaluate it in terms of height, but there are some sometimes when I sky it. Usually your looking for a balloon later in flight that indicates a spin rate that is too high thus leaving yards on the table in terms of carry and roll. I have a tendency to hit it high sometimes, but I don't see the ball balloon mid flight. I'm gonna wait for a few months and see where what the tendencies are and if I still think it's too high I'm just gonna tip the shaft a 1/4 to 1/2" to lower the ball flight and stiffen the shaft.