Our original C-22 had a full marine head with a 12 gallon bladder tank under the V-berth. And I thought I wanted a full marine head also on our current MK-II because it seemed like I had to always empty the porta-potty tank. I even went so far as to buy a new marine head that was a take-off on a new boat that the owner wanted an electric fluch model. When the porta-potty crapped out just before an overnight race, I purchased another porta-potty with the 5 gallon holding tank. What a difference this has made. And for that "other" call from nature, we keep a supply of Wag-Bag's onboard, and slip those over the bowl. You can safely and legally toss the wag-bag in the dumpster. I'm over my need for the full marine head. The porta-potty with the larger holding tank is working out well for my wife and I,(and an occasional guest).
Don