Thanks, that sort of agrees with what I was trying to say. In a perfect world , i.e. perfect release and perfectly matched shaft a button with a spring would not be required as the arrow shaft would bend the correct amount to avoid any unnecessary contact, but something would be needed for it to initially rest on and do the initial guidance. My thinking is that whilst the arrow is in contact with the button and it is weak a stronger spring is used to reduce the flex, and when a stiff arrow is used a weaker spring is used to absorb some of the flex, however I'm happy to be corrected
So my thinking is that if an archer uses the plunger to adjust windage they have changed how much of the flex is being absorbed, and at the same time changed the centre shot.
PS I shoot trad off of the shelf and agree totally
Ah, yes. People misunderstand the whole "flex thing". That's not why spine is used for matching. So long as the shaft bends a bit, how much it bends is nearly irrelevant (so long as it's not extreme). But the bending frequency
tends to go with stiffness, and when
the shaft bends (the point in the cycle it's at when it passes the bow) therefore goes with stiffness. It's not how much it bends, but when.
Thing is, you can't change that frequency with the button.
You can alter the starting point of the cycle, and speed at which the shaft passes the bow, with draw weight and BH. String weight and shaft weight (point or back) also have some effect on that. You tend to see these thing referred to as "dynamic spine" but it's really just fiddling with the matching of the system, nothing to do with spine.