[cart around]

For peace of mind, switching B, and D will accomplish what you want to do. But, that is just a big copper switch. It flows current in both directions. It really shouldn't make any difference which way it's flowing.

If we stick with your theory that it's an electrical problem, I would check the voltage regulator. Put the cart up on blocks. Put a meter on the battery terminals, and run the cart in each direction. See if forward is putting out a lot more voltage than reverse.

I only say that because a few years back there were a few threads on newer carts that had bad voltage regulators, and were bogging the carts down. That stuck in my mind because it seemed like an odd thing to happen.