@catdad1 yeah exactly what I might do. IH advised against it, but I'd rather have something that fits well. I don't care at all about perfect stitching. There is a denim tailor in my area that is really good.
Most shirts (not just IH) are designed to fit big in the middle, narrow up top or just narrow or big all the way through. Athletic cuts are difficult to come by in this market so a tailor is really the best option.