Which prop is best ?

[Revin1]

I have a 21 Liberator that is running a 300 merc promax with the box recurved to rev to 6700
Here is what i have tried

Labbed 26p Bravo with vent holes: Good out of the hole and runs ok but top speed is only about 80-84
Balistic 27p: Terrible out of the hole, ok mid range top speed 84-86

Mazco 28 repitched to 30: Ok out of the hole terrible mid range but will run 90's. I think something is wrong with it because it vibrated bad so I need to get it checked out

I know there has to be a better prop but what is it ?

thanks for the help

[Ted March]

I woulld call Ron Hill.