@JK230SP Thanks so much for all the details! Definitely agree on the speaker placement and will keep that in mind. As far as not killing the batteries, the shop that the previous owner of my boat had a battery isolator solenoid installed, with the trigger wire connected to the ignition system. With the engines off, and key in the acessory position, it wouldn't trigger the solenoid and bridge the batteries, effectively keeping them battery with the sound system separated from the rest of the circuit. That way, if I had the sound system running for hours and it kills the battery, it just kills that battery. Once I turned the key to turn the engines on, it would trigger the solenoid to then bridge the batteries so that, 1) you can turn the sound system back on running of the second battery and, 2) With the engines on, can recharge the flat battery. I reluctantly removed that but I plan on reinstalling it.
When you mentioned having an onboard balance charger, do you happen to know who makes it? Especially with subs, although they're relatively infrequently used in songs, when they are they pull a lot of power rapidly. Great to have a device balance the electrical load between batteries, but from what I read, that's more for more predictable and consistent power draws, like turning on high intensity lights. But with a sub, it's the rapid power draw that I'm curious how they addressed. It's not a major problem you'd notice and everything should function if given voltage between something like 8-20V. But since I just enjoy designing circuits and built some high precision ones, I'd want to install some hardware to ensure voltage remains between 12-14V. I only ask because with my system at 70-80%, using a cheap voltmeter, my voltage drops from 14.4V down to 12.7V right as my sub kicks in, fluctuating based upon frequency, then slowly going back to 14.4V when not needed. With your sound system almost 6x more powerful, would think they'd account for that, unless your fusion amps already take care of it. If you have your sound system with the interior lights on, if you don't notice the lights dimming when the subs kick in, then it's not a big deal. Hopefully this weekend, I'm going to take my actual circuits equipment to see how bad it is.
Honestly, circuit wiring is what i'm most knowledgable in and the best I can do, especially since I don't have much experience and skills working with fiberglass or tools to cut out speaker holes. My hats off to you
@DooGuy and would love to hear your advice on how you approached cutting into the fiberglass and getting a clean circular cut.