Andrew,
No, when you increase the diameter, the RPM's will go down, even if you decrease pitch by 2 inches. In fact, I own this exact engine and I run a MAS scimitar 12X6 on it and it is a perfect combination. You will love this engine. One of the smoothest running engines produced....
After a gallon or two, lean up the low end a tad (all saitos are rich on the low end) and it will start sipping fuel, at around .5 oz/min....