I use a somewhat "unorthodox" solution... Standard schedule 40 PVC pipe of the appropriate id. All my msd waste connections are run in 1-1/2 inch pvc at around $0.50/ft. Fittings (sweeps, angles, tees, etc) run about $1.50 ea.
Use a 4" piece of sanitary flex where ever I have to transition to a barbed hose fitting (eg: head
fitting, thru hull
, easy, and best is PVC pipe is impervious to waste odors unlike even the best "marine" sanitary hose.
Water and vent lines are run in 3/4 inch pex with copper crimp rings.
Total time to install new Type III MSD on Solitaire 45min including new deck
fittings for pump out and vent.. Total cost including deck fittings < $50.00