the motor you are running is very nice..
i used to run the LRP x11 3.5T with 5 cell IB4600s
i would seriously consider going to another LRP motor, but in a lower wind.. either an LRP x12 4.5 or 5.5T
this at least gives you options.. different conditions might call for a slightly less powerful motor etc
it would also allows you to run 6 cell and maintain the same or just a little less power as you have now
also, the LRP x12 motors are VERY nice.. excellent motor in performance and design