Dave, I could shoot your gun no problem. 1 1/2 DAC is right on the money for me shooting 16yd trap targets,I too like to float the target. That why some of my flatter shooting doubles give me fits at SC! Was just curious if you actually see a figure 8 with any of those stock dimensions.
I know as I raise the comb on my gun I begin to see rib between the beads.
So it stands to reason a higher comb or a longer face would require the bead be closer to the muzzle to get stacked beads. A mid bead is very functional if properly set for the shooter. Canting the gun left or right or raising the head causes the figure 8 to fall apart,it can serve as an instant gun mount check before calling for the target.
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"Double guns are a sport and a pastime built into a beautiful package to which I attach myself when entering the great theater of autumn, those days now grow more precious because we are given so few".. Robin Lacy