Making myself a new long sleeved shirt, and decided to be adventurous and put upper and lower plackets in the sleeve opening, rather than continuous lap as I've always done. It wasn't nearly as hard as I expected. Someone here (I can't remember who, but thanks!) recently mentioned Connie Amaden-Crawford's book, Guide to Fashion Sewing, and its illustrated instructions were very helpful.
Of course, it did temporarily dampen my enthusiasm to find that I'd inserted the plackets for two right sleeves. *sigh*
Doreen in Alabama