Nice mods Randy. I had a tank flusher connection on a Class C and used it. It is a lot easier that filling the waste tanks from inside the RV to flush plus it shoots water in there under pressure.
Did the sewer carrier affect your ground clearance much? I like your idea of using the larger piece to hold the end fitting. That is often a problem with hose carrier units. I've had to file down fittings to make them fit and it limits the choices in fittings that you can make.
I'm going to add one or two pipe type or tube type carriers underneath on my van. Hopefully one will carry a rolled up outdoor mat. I had not thought of using vinyl deck post covers as carrier units. Good idea.