Hi K,
The propsizes are from my experience with this size motors and the rpm's they generate on 4S, (rule of thumb so to say).
If you go up in Voltagem reduce the propsize untill you're syre the motor, Lipo end ESC will cope without overheating, than go to the next size prop.
For a surface piercing drive, you'll want the prop at 10-13% of the hull length behind the transom, so that's the size stinger you'll be looking for.
To counteract propwalk, you'll want the rudderblade next to the prop, as in the picture of my 65 cm BK Xcalibur;
Sideview:
To be honest, I would not go for a more powerful motor, your hull won't cope.
The Xcalibur in the pictures has an epoxhull, very stiff and runs up to 65 - 70 km/h (40 - 44mph) on smooth water and is a handfull to steer, with a wobbly plastic hull you'll be more floating upside down due to the bad handling...
The boat on the left is the Xcalibur, accelerating out of a turn:
Regards, Jan.