My 1.6m Monolog 70 has HS-7975HB on all four. They have specified operating voltage of 4.8-6.0V. My ESC has a programmable BEC.

Is there any reason not to up the voltage from 5v to 5.5v or 6.0v?

I'm not sure if would benefit or not. The servos are all standard size and some planes that size uses mini servos, at least for the ailerons. So I might already have enough servo power.

-Ken aka l2t