To go back to the original question, an FAA wonk told me years ago that for the vast majority of multiengine aircraft, the ideal bank with one out was two and a half degrees. The five degrees is a number for certification. Because of people like me, most training is done with no bank, since that is better then five or more degrees. I had a an instructor on the whale tell me that it holds true there. Unfortunately, I can point to nothing in writing.