Steve,
Since you have a MkII, as I do, I thought to mention this.... when I bought my boat (new in 2000), Catalina plumbed the discharge hose leading to the holding tank through a maze of twists and turns. It led aft from the toilet into the cabinet, then did a 180 bend forward leading inside the area that is between the hull and toilet...passed through the hanging locker next to the Nav table, then into the holding tank. The hose seemed to run a distance several times longer than just a straight shot forward to the holding tank. Go figure how they ever came up with this?? I re-plumbed the hose to run directly forward from the toilet, passing through the hanging locker then into the holding tank. I had a ton of hose left over after I did this. It just required a hole drilled through the wall between the head and hanging locker and turning the outlet connection leading out of the toilet.
Just a thought since you might have the original hose routing scheme from Catalina.....