That sounds a bit dicey to me. One spark from the battery and POOF no more SailorBill!! Is there an airtight bulkhead (wall) separating the fuel tank from the battery?

This sounds like a design situation to me.
Sometimes designs or innovations on boats will work in theory but not in practicality. My advice is to contact CL Sailboats with this question. I'd also recommend you get in touch with someone who can construct an airtight battery compartment for you. As well try to see what you can do to ventilate the lazarette better so the gas fumes will escape.

I may sound too finicky here but when it comes to safety (especially when a life could be put in danger) I don't take any chances. I hope you find this helpful.