Flight Risk(custom 24' cat) briefly supported a biplane rig before I owned it. It was being used as a test bed for the concept, the owner was contemplating a 65' cruising cat with that set up. Worked quite well, lower center of effort, no heeling in our testing, great simplicity with no headsails, which was his quest. Only the windward rig was powered up in a beam reach, but the leeward rig was quite docile, and the boat still moved nicely on that course. Both rigs outboard on a dead downwind run was great. Probably not as high performance as a sloop rig, but great for recreational sailing, worthy of more experimentation in my eyes.