I don't run Saito's, though I just received my first that I will be installing, but with all of my unpumped 4 strokers ( Mostly O.S.'s) , as long as the fuel tank mid line is not too far from the carb spray line, the plane doesn't care if it is inverted or not.

I tend to run most of my engines inverted as well, and the only minor problem tends to be with a slightly tighter tuning window, and a tendancy to siphon once the fuel level is high.