"maneuverability" is only an additional modifier. Maneuverability showed in the ship info screen are based only on "mass" and "steering_power".
It's worth to know that perks which modify maneuverability work only with "steering_power" parameter (the same for modules). Look into perkDispatcher.script:
Code:
function ModifyShipSteeringPower(pilot, steeringPower)
----//----
return modifiedSteeringPower;
end;
Function takes only actual "steeringPower" of pilot's ship and returns new steering power.