Some thoughts on adding the Vacuflush. Use better components than what comes standard with Parkers. The Vacuflush systems are better so at least you are thinking about a better quality head than what comes with the Parkers. The Parkers system doesn't have a separate 'water-in', 'water-out', flush/dry-bowl switch. We have the factory electric head on our 2013/2014 2520 XLD. We don't use it, mostly because Parker (and most other production builders) also use cheap head hoses that are vapor-permeable, as is the 'plastic' holding tank. It's hard to not have 'head-odor' with a set up like this.... Our last boat had an 80 gallon stainless steel holding tank, and non-vapor-permeable hoses, after modifying them with Hardcast Foil-Ray butyl-sealant tape; we had no head odors. We also installed Raritan PH II heads. (we had two heads). They were one of the best available back in the 1980's.