I raced my 09 NT1 for over a year an did not use a regulator, I won more races without a regulator, I ran the bls451 and 351 and they worked fine with my 7.4lipo, I wouldnt run low quality servos without a regulator, but these high end servos should be fine be sure to set your end points perfect and if your not comfortable then just run a regulator be sure its a high amp regulator that run no less than 5amp.
cheers