Absolutely 4 squares is adequate, even with single ply actually, 3 is not enough for me. I used to be one of those who would roll off a handful but when i got the Airhead it just made sense to dial it back and found it very easy. I'm sure some peoples diets make for more of a mess to clean up...
I have an older Gemini catamaran which i bought in Connecticut and while it had a 14 gallon holding tank immediately ahead of the throne ( so short hose runs) it had a y valve which allowed for pumping to the tank or pumping overboard but no provision at all to pump out at a marina. I removed...