Co pilot is for the electric drive motors. Unfortunately, they don't make them for cable drive systems like your Maxxum. They make them for the PowerDrive, PowerDrive 2, Terrova, Riptide ST, etc... Sorry for the bad news. I hope you get your trolling / back problem figured out. I know what a pain it can be (Pun intended - and I'm very sympathetic to your situation - I have the same problems lately.)
I would HIGHLY reccomend looking into the I-Pilot line from Minn Kota. It is by far, the best investment I have made in my boat. I actually removed my pedal and I now have that much more room on my front deck. Everything it controlled via remote control that you can hang on a lanyard around your neck, or just hook onto a belt loop like I do. If youre comfortable with the pedal, you can keep that on and use that as well. Do some research on the I-Pilot. You will only have to get out of your seat to lip in the big boys you cant swing in!!! Just my two cents.