I would not use the Arc system, for many reasons. I would install a dual battery setup. Its much simpler and cheaper and a combiner can be added at a later time. A conbiner will charge ether battery, no matter which battery is in use.
With the Arc system you can not start your engine on ether battery alone. With a dual setup, you can and you will know that ether battery is up to the task. Giving you full control. On smaller boats, its very hard to seperate house loads to starting. Another reason were the dual setup is good for.