OK quick update, the toilet fits, I have not secured it, or the venting, completely but I'm moving ahead with drilling holes. It's pretty tight and the toilet has to be taken apart to even get it thru the door but the whole thing sits on the ledge and there is room for the vent on the side, spider turn and all that. See attached image.
Plan is to find a PVC angle and get the hose up to the side of the roof as close to the wall to aft cabin as possible (we have 2 cabin version). Then we'll have a clamshell on side to cover for rain. Roof vent is not option as it will vent into the cockpit enclosure which seems less than ideal.
Also it's unit is pretty tall, the Air head might be an option as it's smaller but I'll have to say that the angles sort of helps this fit as it gives the fan some open air on left and handle slides along wall, I'm not sure the handle on the Air Head will. Once installation is complete I'll make some more pictures but I'm quite relieved that it fits.
Mrs now has plans to convert the space behind it to storage for coir and composting accessories. Her idea is to either finish the interior or possibly mount a small built in "cabinet" in the fiberglass piece that covers it, my idea is to put the cover on and have a beer.
Edit: Read the comment about the door, I tried my best to simulate usage and was able to close door just fine, I'm 6.3.
Cheers!