I was trying to stay out of this because I already know a bit about it ( In fact its my suggestion to post the question)
Why would the OP want to have it six feet away? If concerned about height above the waterline, only the end of the 'air vent' pipe, 1/4" dia needs to be high up
I think the OP only wants to put it 6ft away because he has identified a convenient location for it that happens to be 6 ft away. Also its not my understanding that he is putting it in the heads compartment, rather on the bulkhead that forms the heads compartment. In the heads compartment where it can easily be seen sounds like bl**dy good idea though!
However it is this statement which is wrong
"only the end of the 'air vent' pipe, 1/4" dia needs to be high up."It is the top of the loop that must be the recommended height above the waterline. It would not help if the vent tube goes to the top of the mast, if the loop is not above the water line it can still syphon.