There have been a variety of improvements made to the head. Improvements submitted as a project can be opened by all users. Improvements submitted as a Tech Note can only be accessed by C34IA members.
Fresh Water Head and Overflow Control
I got a little tired of the Head Overflowing when someone forgot to leave the handle down. I decided to convert the smaller starboard Fresh Water Tank to a dedicated fresh water supply for the head. The starboard water tank is about the same size as the holding tank. This is great because you reduce the risk of overfilling the waste tank. I added a 1/2" Tee off the inlet sea cock and put a 1/2" ball valve and a one way check valve on the fresh water inlet side of the Tee. Then disconnected the stabbed fresh water tank from the fresh water supply system and ran a direct line from the water tank to the Tee. Then connected to the head inlet line to the other side of the Tee. End result and benefits:
I don't need to use the inlet sea cock. It stays shut. I only need to open the ball valve to the fresh water tank.
The head never overflows. The top of the head is is just a little higher than the top of the water tank.
The head odor disappeared or at least is better. You don't have all those sea water microbes dying and causing additional odor.
We only use the large stern water tank for drinkable water. We use it more and this keep things fresher. R Norquist
Fresh Water Head and Overflow Control (version two)
Another option is to tee the sink drain hose just above the thru-hull and connect that to the head. With this setup I normally keep the thru-hull closed and after using the head I run water in the sink (while washing my hand for example) and then pump that water through the head. This allows me to keep my thru-hull closed and get fresh water in my holding tank. I also don't have to worry about head water/bugs getting into my fresh water tankage. When I'm offshore I can open up the thru-hull and everything works as normal, the sink drains overboard and the head get seawater which can either go to my holding tank or overboard with my head Y valve turned.
Hooks in the Head
An advantage of having the head aft is that it’s a great place to hang wet foul weather gear to dry using engine heat. (note the Caution placard mounted on the alternator access door) My First Mate pointed out that another C34 owner had built some overhead coat hooks in the head. Our folding wardrobe hook could really only hold one hanger and we needed more hooks.
While measuring to install a piece of teak on the overhead, I noted placement would be difficult because the port side coach top winch mounting bolts were in the way. Then I realized that a simple “eye nut” mounted on a couple of the bolt ends might be a simpler fix. I found some stainless eye nuts at a local chandlery that fit perfectly. They were ¼” diameter 20-thread size with a ½” eye @ $3.85 each.
I removed the “acorn” finishing nut and retaining nut. Then I reinstalled the eye nut. To get the eye nut snug and still be facing thwart ship, you’ll have to play around with one or two small flat washers to get that proper orientation.
We now have three convenient hooks for hangers in the head. Tighter squeeze, but the head is still usable while drying gear. I even installed an eye nut on the port side in the main salon for some future use.
Additional head storage 1991, Nov.
Changing a Shower Drain Hose 2001, May 
Cockpit shower 1991, Feb. 
Enhancements to a MKII - Lectra/San 2000, Feb 
Head Drain 1995, Feb. 
Head problems 1991, Nov. 
Head solution - antisiphon 1992, May 
Helpful Hints: head upgrade, stuck macerator 1998, Nov. 
Hooks For Hangers In The Head 2005, May 
Interior mods: teak head grate 1995, Nov. 
Raised toilet (in Dinette mods) 1993, Feb. 
Shower Curtain Replacement 2003, May 
Toilet repair - new seats 1999, Aug.