Pilot hexapod gps

Hello Folks,
recently our team are developing a jant hexapod, 2 meters…first we bought a frenovo hexapod to know the software about walking.
it works with raspberry and have 20 servo with signal pwm.
now we have a emlid rtk base and rovere antenna with navio 2 but this have only 14output for servo.
i want know which expander i need to control from I2C port navio to controll 22 controller that movie 22 servoactuators with signal dir pulse enable.
Better continue use navio o normal gps antenna on the raspberry and command 22 servoactuator from raspberry?
thanks all!