Flaxen: I agree with Enigma. If you've got the time, take the rotor head off, disconnect the servos from the swash and check it out. Can it slide up and down the shaft OK? Maybe something got stuck there, and if that was the case then it would be able to tilt easily (little up and down movement) but pitch would be hampered (lots of up and down movement necessary there). Have you tried swapping to the stock battery right now to see if it works fine, and then when you go to the LiPo it's not working? If so, that'd be VERY strange and I'd contact Horizon.

Mark: About the brushless conversion: I don't see any way that that could weight LESS than the stock Blade CP with battery at 285 grams. My blade weighs in at just under 300 grams (10.5 ounces) with my 900mah LiPo, and I had to go DOWN to that battery pack because the 1320 was too heavy for efficient flight. I'm now using a JR 610 UL Ultralite FM Receiver (as of today!), a GWS PG-03 gyro, Eflite 2-in-1 unit for speed controls and the stock servos. Since he's using two Phoneix speed controls, that'd add a bit of weight, compared to the 2-in-1 unit which contains both speed controls. However, if it IS do-able, then that's something else I'll have to consider

He's using HS-50 servos, and not HS-55's? Actually now that I think of it, those servos are so light you could lose a few grams with them, but I think they might be a bit overworked in rigorous flight, they're not designed to take much stress. At the LEAST I'd use HS-55's. Also, how is his tail rotor system working? Does he have a tiny, ittty-bitty micro brushless motor driving the tail or what? And how does the tail motor ESC get its power if the battery plugs into the main motor ESC (I'd assume)? I think for the best efficiency you'd get a Phoenix 10 for the main motor but use a brushed micro speed control for the tail motor and leave that alone, makes the most sense to me and it's the cheaper way to go, less modifying involved because you're not getting a new gearbox housing or anything. This is something I'm going to have to do a little research on, hehehe.