When I installed the new holding tank last year when the boat was on the cradle everything looked good and level for the vent line, hose from the toilet to the holding tank and the discharge hose used for pump out which were located on the forward side of the tank. Once in the water with the boat was sitting with the bow riding higher, the tank was not level and tilted away from the discharge hose. We were not able to completely pump out the tank.
Original hose locations
So I bought a relocation kit from the tank manufacturer and moved the discharge hose to the opposite side of the tank.
New discharge hose location
New access hole needed to install new discharge hose connector
All done