Great project! I always liked that particular X-cell fuselage..

tail servo on tail? I don't know that that's a very good idea.. I mean, think of all the vibration back there, for one! also, since you will be using a pushrod, why not make it longer and put the servo by the frame, rather than putting it way out there, with more connections to worry about? Also your heli might become tail heavy, and it would take a lot of weight to compensate for it in the front! I think that since you are going to be using a pushrod (I mean, just stating that it exists), I think it's better if you make the pushrod longer than make the servo cord longer with an extra connection that may fail.

Also heard something about possible interference if the boom is metal, and having a long servo wire, but I'm not sure about that. It would cost a lot to make sure it wasn't true though!