I'm sure lots of people love their composting heads, but I can't stand them. I was living on my boat for a few months and had a composting head
and it was a constant misery.
I can see it working great for someone that only visits their boat once or twice a month but if you live aboard it can't compost as fast as you putting stuff into it :P.
Even with all the peat moss it pretty much ends up being the same (smelling) as pooping into a five gallon bucker with no lid and leaving in your boat.
Also you'll be emptying the piss pot (and I had the special larger one) every day or two and you'll have to clean it with bleach or else it'll stink to high heavens.
While I was living aboard
I would've given anything to have a holding tank
and seen as how your planning on doing alot of off shore sailing emptying it won't be a problem... but emptying a composter will be a shi**y situation every time.