How does the Max 5 prop compare size to size to a bone stock old casting P5X? Or even new casting if that's what you've tried...

I have an old casting P5X that's been a magic prop for me, great getting on plane, great mid range, and best top speed so far of all props I tried (Labbed B1 30 , Cutting Edge 5blade, Hering 6 blade 28p, new casting 30p P5X, etc)
But I need to pickup another 200-400 RPM to be in peak HP range. I got a 28p old casting P5X to try but afraid it's going to be too small... And I really want to try a Max5 but they come in so many pitch sizes, I want to make sure I'm chosing wisely.

I know going down 1" pitch typically gives you 200rpm, but not sure if prop to prop the Max5 rev differently even at the same pitch size. Need to know where to start off compared to my P5X

Thanks in advance