You need more bow lift that is why your getting the porpose.It can't carry the bow and it falls it's better in rough water and worse in flat right? You can try to spin the drives in that might help. I would try to find a set of 16.5 x 25 or 24 three blades that would probably work. It's going to be hard to find props in the smaller pitch sizes in the 3's they are just getting hard to come by.

Which would be better to 4 blades or 3?

Would the 4 blades carry the bow better? Would 16 X24 4 blades be better than 16.5 X 25 3 blades?

Depends on the prop, they are all designed for different lift, bow/stern/neutral. I personally would try the 4 blades first, depending on what they are. I am running 3 blades, and get a bit of porpise at slower speed because they cant quite carry the bow and it falls on its face. Throttling up past that point makes it go away. I was told 4 blades would help a lot (Bravo 1's)

I have a 271 sr-1 Formula that I'm going through the same stuff right now I have a labbed 24 B1 4 blade that does no porpose and a 25p Mirage that is porposing and I just Overreacts to trim in the rough stuff. Top speed is better w/ 3 blade but overall I like the 24p Bravo One. IMHO

you want the biggest diameter the boat will allow meaning that you want to keep in increasing the diameter until the boat starts to chine walk or act stupid. when it does this, it means the stern is lifting to much. i will explain more later, have to run...

The only problem I think your going to have is if you can't spin the 26 x 15 3/8 over 4200 your definitely not going to be able to spin a 24 x 16.5 5,000. I think you might have a 1.3 gear ratio.

have you called pantera yet???? those guys have been around longer than almot anyone in the business and im sure they can help you out....

Try one of the prop companies... BBlades or ThrottleUp.

I do have the 1.3 ratio. Is that what you have to excal?