The head bulkhead is at top, the holding tank bottom. There is a crash tank, also sealed, in front of the holding tank. It was the speed sending unit, lowermost in the picture, that leaked due to a faulty o-ring.
While not always practical, why not put the through hulls in a bulk headed compartment? On a monohull this could be practical either forward or aft, or by running the bulkhead up the side. You do have to hang down to service valves, and opening them is not very handy (extensions can be fitted), but it is safe. During the homecoming trip we flooded this compartment right to the the water line without ill effect.