You are getting on the plane quickly with a big load because of the "ski" prop. It probably has a lowish pitch and hits your max revs at a lower speed. With a big load on board, this might not be the worst thing ever. And you have a big load on a SR4 with a 40hp.! A longer pitched prop should improve your top end, closing the flooding hull will help your hole shot with the bigger prop, but make your boat more unstable at rest. Don't expect too much from the 40hp - I'd guess that properly propped and running light, high 20's is your lot.
The easiest way for you to check revs is probably a Tinytach
Yes, the MPG question is a bit silly. It sounds like you'll be at Wide Open Throttle most of the time, so WOT consumption for a Yammie 40hp is what you need to know!
EDIT: What Badbaws said about trim