Fish n' I'm just waiting for you to perfect one and report back because I have the same desire. I also would like a large trap for the CC.
One of my thoughts was to use a plastic 55 gal drum, cut the bottom end out and put the mesh cone in that open end. The other end would be a removable lid end. Then drill holes with a step drill all over the rest of the drum for water flow. Connect some of the holes using a jig saw to make slots big enough to let most BG out but slim enough to keep the larger cats in. Place it just off the dock with a rope attached and a 2" pvc pipe going down to the trap to introduce feed.
Feed through the pipe each day with the removable end off the drum for about a week. Pull the drum up, put the lid on and feed inside and see if it worked.
The other idea I had is take my 42" square fish holding cage and put a sliding gate with latch on the bottom edge. Take the floats off the cage so it would sink in about 5' water at the edge of my dock. Use a 2" PVC pipe to drop feed daily for about a week with the trap door open to get the fish used to going in. When I wanted CC, drop some feed in, wait till I saw muddy water and activity, pull the trip rope to drop the sliding gate.
I got plenty of ideas. Getting ones that actually work and actually implementing them is another story.
