The design is really simple. Two pieces of aluminum shaped to clamp on the barrels. One set clamped where the front bead would be and another set clamped approximately where the center bead would be. The top piece of each set extends out to the left far enough for your line of sight with your left eye when mounting the gun right handed. It really looks so simple. Judgeing by the results the Dave qualified for the last October and again last April, I guess it works quite well.
Tom

Here is the "Parker Gentleman" Dave Fjelline at the Spring Southern.


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I have been using this system since about 2004. I have used a homemade system as well as one sold by an Arizona shooter. However, I have put them away since I have converted both of my over under competition guns to crossovers. My side by sides are also classic crossovers.