x2. Which prop w/ 4000lbs????

Ok i have a 2007 mastercraft x2. The prop on it now it a 14.25x14.5. Its top speed is about 39 mph and that is at 5300 rpms. It has stock ballast, plus the up graded fly high system(it has the xstar sacks in the back insted of the x2 sacks, and has integrated bow sack) If it is only my dad and i, i like to add more weith. SO i put a 750 in the front walkway, and a 600 as far back as i couild on the ground. Then i also added a 400 in the very front of the boat. I know this is alot of weight but the 750 sack prolly is only 500. ANyways the boat would never get on plane. I was wondering what prop one would reccomend to get it on plane and what this new prop would do to overall speed, performance, and gas consumption. I know this boat can handle this much weight because i have had the fly highh system slammed and seven people in the boat. THe only problem was it took five people in the front of the boat to get it on plane.