Our '66 Trade Wind has an 11 gallon black tank. I know for sure (it' a new one) so I bought an 11 gallon blue boy. So far when boon docking the blue boy collects the gray water. We usually boon in forest campgrounds and use the public potties in the day and the on board potty for night use. No flashlight trips at night for us. The black tank takes 4 to 5 days somestimes more for the 2 of us with this plan.
Neil and Lynn Holman
Kirk Creek, Big Sur, Ca. coast.
1966 Trade Wind
1971 Buick Centurion convertible
1969 Oldsmobile Ninety Eight