Yes, I realize that. But, what I had on hand was the 15-4 and what I was looking for was to see what differences in the vertical I would get with the 4" pitch. I am going back to the 15-8. As far as I am concerned, the noise differences far out weighed the benefits.

I have a box full of props ranging in size from a pretty small electric power prop to a 16-8. The 16-8 is for my OS 1.20 AX which spins that very well with a minimum of noise.

The point of my post is that decreasing pitch has some down sides to it. And, as you pointed out, increasing the diameter helps in that respect. But, again, even with the collection of props that I have accumulated over the years, and it's fairly considerable, what I had in the size range for the OS .75 AX was the 15-4 and the 15-8. I have smaller diameter of course, but that would be a waste of time on that engine.

CGr.