Why not a false bottom covering the whole bottom? I've never fly sparge, but I recirculate and I'm mindful of channeling. To date I've tried a smallish domed false bottom, a bazooka tube, and recently a custom false bottom designed to completely cover the bottom (precise fit). The best for me has been the full false bottom.Totally agree, Jim. I DO fly sparge, and the full domed false bottom is the ideal way to go if you ask me. Palmer CLAIMS a ring dividing the area is almost as good at preventing channeling, but full FBs are so easy to get now it's worth it. The gold standard. Just make sure it comes with, or you modify it to include, a draw tube leaving zero dead space. I leave only about 1/2 cup liquid in my 10 gal cooler. Those that draw near the top of the dome will kill your efficiency.
I have tried both the 10 inch hat shaped false bottom and the full width hinged false bottom (Sabco), and was expecting to pick up a few points with the full width bottom. It didn't happen.