I have the same airplane and it did lack power with the Supertiger 51. I bought a Tower hobbies 75 and the plane came alive. Offcourse, the plane could go faster
Anyway, I would give the 75 a try. Here is the link:
http://www2.towerhobbies.com/cgi-bin...?&I=LXUR78&P=0
Good luck,
Le fou