A few things you may not have thought about
If you bought the larger 5-6 gallon model, the tank will weigh upwards of 50 lbs when full....a LOT carry up the ladder into the cockpit
. The tank in the smaller 2-3 gallon models weighs 20-25 lbs when full...not quite as bad, but still not light.
The pumpout boat is gonna charge you a minimum amount to come to your boat whether they pump out a little or a lot...if it's the smaller tank, you'll need 'em twice as often.
Pumpout hoses drip and sometimes spit up...if the tank is in your cockpit
, that hose is gonna drip or spit up in your cockpit.
When you add all that up, you just MIGHT want to rethink your "no deck pumpout fitting" plan. Installing one is easy and inexpensive and will prevent far more "head aches" than it creates.