Funny I found nothing in this question pertaining to "trim"!!! It seems there are a lot of people that are under the assumption that everybody has the same windows all over the country. There`s no "cookie cutter " answer. Caulking is a good viable option. It`ll stop your drafts, but it won`t do a thing for your R value. With out knowing the aspects of the installation, it`s pretty difficult to give a viable solution. Don`t discount the energy auditor. I`m quite sure he did`nt just fall off the turnip wagon!!! If you doubt his word, ask for credentials. Some times the most difficult sounding solutions are the best and easiest.