Dual GPS Question

I am thinking of adding a second GPS unit to my Pixhawk powered hexacopter.

Do I need to run through the hardware configuration again, or just modify the parameters as described here? copter.ardupilot.com/wiki/common … ommon-po….

There is no problem using a second GPS on Pixhawk but you cannot add an extra compass.
Just connect the second GPS to Serial 4/5 and set the parameters as for your current GPS.

You cannot use the compass, on the added GPS unit, as it will give address conflict on the I2C-bus if you don’t have a device where you can set the I2C address. Unsure though if Pixhawk software will detect a third compass.