While I was deployed to Iraq I bought a couple of Wista 6x9 roll backs to use with my Cambo 23SF. Now that I'm back, I tried using them today and discovered that they will not lock into place on my Cambo 23SF. My Horseman backs work just fine. I am a bit surprised to find that the backs will not lock down. Anyone using the Wista backs with a 6x9 view? Ideas? Thanks!