When we thought we needed new props we called the best (we were told by many sources) prop shop in Seattle and asked them what information they needed to determine the best props for our boat. They said they wanted to know the make and model of the boat, the type of engines, the horsepower of the engines at max rated rpm, the rpm of each engine at WOT, and they wanted to see the current props.
From all this they could determine the best props for our boat. How this compares with the chart or formula on boatdiesel I have no idea. But since props are expensive and the potential penalty of installing the wrong ones could be even more expensive it would seem to me that the smart course of action would be to turn the matter over to a qualified and experienced prop shop where their work is backed up with a warranty.
In our case the shop found on examining our current props that they could be extensively reworked to achieve the proper performance. Which cost us several hundred dollars instead of nearly $4,000 for new props. An Internet forum is not going to present you with this sort of solution.