What you have should be plenty. I would look at reducing rotating mass (drivetrain) and also at higher quality bearings, also make sure your drivetrain rotates freely.

Also, play with your endbell timing and gearing. Possible you need to go down a tooth on your motor, and/or reduce timing. Likely 35-40 degrees is at the upper end or beyond the efficient point of the motor. Going down a tooth will increase your 'punch' and only slightly reduce top end speed.