That engine should easily launch that model -- I suspect that the mixture is VERY rich (can't be lean or it wouldn't run). Try turning the NV in a bit & see what happens. If the plastic limiter interferes with your attempts to tune the motor, get rid of the limiter.

An FXi with an 11-5 should hit somewhere near 14,000 & push that model to ~ 70 mph (without the aero-aids).