So not a terribly exciting update, but here is my weekend project.
Making mounting brackets for the Minn Kota charger. It's a simple bracket spanned between the firewall braces. I just used some 1" right angle aluminum channel, and 7/8" P-clamps.
The next step will be to make a plate to hold the batteries in the existing battery tray and route/connect the wiring to the charger.