People underestimate the difficulty of doing a "common everyday inside loop" precisely! There are many factors involved and the inside loop will allow these factors to show their influence. There was a great article written in the May 2005 issue of Model Airplane News magazine discussing trimming and I suggest seeing if you can get a copy somehow, or maybe the article can be accessed on their website. The article is so good, however, repeating what it said here is more time then I'm willing to take.