Pixhawk 1 using Ardupilot rover setup for Boat with 2 parallel motors

Looking for help with setup of Pixhawk 1 with Ardupilot for Electric boat with 2 parallel motor. I used Rover set for skid searing. I have 2 bidirectional speed controller with power by lipo 3 cell to power mode. Speed controller are connected to channel 1 and 3 as suggested by ardupolit doc. They suggest RC input for Throttle Left and Right. That works but do not like the two handed control. Using throttle for speed and direction with the middle being no power and the Roll the searing.
Is this the only setup? I tried using Ch1 from RC to #1 output and Ch2 for #3 output and did mix in radio of Elevator to Pitch and Pitch to Elevator. This works without the Pixhawk and give one stick control. Right stick, forward and reverse, searing. I can spin on own axis. Question can i make the pixhawk do this in manual mode and use hold with GPS to hold position. That is my goal if you can help me.
As a first time user of pixhawk and ardupilot i had many issues getting this far. Main one was i am using a Mac Mini with M1. Mission Planner does NOT work with Mac. I did a work around and installed Windows 11 using software Parallels. Why does Mission Planner not work on Mac ver 13?
Currently i have another issue that the Mode is not configured. I believe i only need manual and loiter or hold. I have channel 5 and 6 for RC working but not mapped to mode on pixhawk.

Better to ask in the ArduPilot forums: https://discuss.ardupilot.org