Hey Paul, Gemini owners unite! We'll take over the world.
My concern about placing the generator on the stern is that there is a wind eddy created by the bimini (hard top on newer gems). The first time I ran my generator I had it on the stern, and I felt a little dizzy. But mine is a crappy two cycle, and probably puts off a lot more pollution than yours. I'm also particularly sensitive to chemical fumes. If you have a carbon monoxide detector you should be fine.
I'd recommend locating the DC ground on your boat, just for informational purposes. My boat does not seem to have one, but then again, it's a grandaddy gem, and has some other design flaws.
Gemini Catamaran Split Decision