OK, there's a lot going on here. It will be tough to paint an accurate picture in a forum post but, I'll give it my best shot. All layouts must be based off of an accurate PAP. In any method (dual angle, Storm PB, whatever) they are driving at the same thing. That is positioning the Weight Block in the ball based on the layout. If you lay a ball out using Dual Angle and then move the grip you are actually changing the location of the PAP relative to the layout and how the weight block is positioned in the layout. So, yes...the numbers will change and therefore the reaction will be modified as well. It doesn't matter what layout technique you use that will remain true. Using Dual Angle, the first angle determines how quickly the core begins to influence reaction shape. So, yes it can be viewed as a measure of length with some respect. The Pin to PAP distance determines flare relative to the balls overall flare potential as determined by the manufacturer. The second angle controls how quickly the ball transitions on the friction.
Now, let's say I lay a Symmetrical ball out ... 4X4. That layout will look a little different from bowler to bowler simply because of the location of their PAP. To simplify the conversation let's assume both bowlers have the same skill, similar rev rate etc., and the same ball with surface and lane conditions the same. The only variable is the location of their PAP implying the ball comes off their hand differently. The layout may look different but the shape and reaction will be very close.
Yes, 3 3/8 is the strongest position for a layout. It is because that pin to PAP distance places the weight block in the most unstable position (45 degrees from x and y axis). That has not changed from back in the day and probably never will.
Please keep in mind that the numbers work differently depending on whether you have a Symmetrical or Asymmetrical core. The difference is due largely because of the strong Mass Bias in Asymm. core balls which has more influence on the ball roll on the lane. Essentially, the MB is the PSA for the ball in an Asymmetrical core ball. Once a Symmetrical ball is drilled the Thumb Hole becomes the PSA (positive spin axis) because it is the largest hole in the ball therefore an area where the most mass has been taken out of the ball. Effectively, making it an Asymmetrical core ball. So, yes, you can use dual angle on the Symmetrical core balls as a layout technique as long as you realize the dynamics of the PSA. This is because undrilled Symmetrical core balls do not have a strong Mass Bias.
Well, long explanation and probably did not really do it justice but, suffice to say that a layout is all about the relationship to the bowlers PAP and that the PAP will vary from bowler to bowler based on their release characteristics.
Fran Varin
USBC Silver
Brunswick Advisory Staff