On a 400 E-Starter, 8.4v nimh batts isn't gonna cut it, and the 9.6 nimh batts will work but only marginally so. The plane really comes into it's own on something like a TP1320 3s lipo. That's what I've been using and she'll take off with authority within 5 feet at half throttle and climb out at 45 degrees and will cruise for over 30 minutes at a quarter to half throttle. Great plane but you MUST have the right battery............