I'de be more worried about the stab or ailerons fluttering. I'de brace the stab and fin and seal all the control surfacers. My Pulse has an OS46AX and it's fast enough. With it's built up tail surfaces I don't think the Pulse is the best choice to go pushing through the sound barrier. Something like an Ultra StickBridi Kaos would make a nice home for the 55.