There is no "ideal"
angle of heel; it all depends on the waves, current, passenger comfort, etc. As a general rule of thumb, sailboats without large overhangs at the bow or stern sail fastest when they are as close to plumb as possible. I have found that with a breeze of between 10-15 mph, with a full main and 100% jib set, this translates into about 10-15 degrees of heel on my Oday 23. I reef the main when the wind is over 15 mph in order to minimize heel and enhance comfort(especially when my wife is aboard). I have had my boat over 25 degrees of heel, and I found the ride to be thrilling, but ultimately uncomfortable. Despite the fact that the 23 is a tender boat (heels early and alot) she is stable; it will take more than just some strong wind to knock her down. I have never done so on the Oday, but there is a point at which the heel becomes so great that the rudder will lose its bite in the water and the boat will round up in the wind. A nice safety feature.