the best way to get the pitch range wider is to drill a new hole on the collective lever where the link to the servo goes. move the ball up about a 1/2" and re-adjust the linkages. Since that lever is not a perfect 90 degree lever, you will have to adjust the collective servo horn to counteract (as best you can) the differential in the collective lever.
It also takes some wizardry on the orientation of the collective and throttle servos to keep them from interfering with each other and the fuel tank.
The other item to address is the tail rotor setup. If you can, get the shuttle plus tail rotor lever set up. It is a lot better than the ZXX stock setup. Also you will want to do something different with the control rod. Runing the stock one through the plastic tube is not good and binds a lot. I also would stay away from a tail boom mounted servo, because the shuttel is naturally tail heavy. On mine I cut down an old Ergo 60 tail control rod and bent ti to shape, and it works quite well.
All in all, when you get the small stupp out of the way, and a decent set of paddles, the shuttle is one great flying little chopper that could!
I came, I saw, I hovered