Good holeshot and efficiency tend to go together. I'd focus on pitch rather than diameter; most prop designs seem to increase diameter as they reduce pitch.
Moving the engines 30" or so aft on a bracket makes a boat much more sensitive to motor weight. The fact that you have to trim 'em down says the boat want's more stern lift but that also increases drag. Putting SE Sport fins on the AV plate will give you more lift, so I'd do that before screwing around with props. And make sure motor height is correct . . . AV plates should be above solid water when you're up on plane to minimize drag! When changing props, you'll want the pitch that puts your WOT rpm near the top of the recommended range with your max load for best durability. If you lug down a 2-stroke motor, they'll build up a lot of carbon and cause the rings to stick which is a long term problem, but if you lug a 4 stroke, you'll burn the exhaust valves if you run it too hard. If I had a 4-stroke motor (I/O OR OB), I'd put a vacuum gage on it and observe an intake manifold limit of 7" Hg at cruise.
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