Ran into that very problem on the last install of the same windless. What we did was to run 1/0 wire, three of them if I remember correctly, inside the
motor cover. I had to flatten them between 2 pieces of boards, being careful to not split the covers, hot water
helps the covers be soft and workable. They just need a little help to make the 2 bends around the motor to the studs. We then added heat shrink for insurance
Those wires were run through the deck
to the control solenoid and breaker which was as close as possible. We then stepped up to the larger wire which ran to the batteries.
I must say that if time and a machine shop was available I would rather make a spacer plate about 2 inches thick. You could use the gasket
for a template.
Hope that helps