I get collar gap in many OTR jackets due to similar issues. I've found some brands that work for me, but have had the best luck with MTM. I've also learned that I cannot get by with short collar points, which are exacerbated by the collar gap issue. You should consider some of Luxire's entry level fabrics. I think they start at $60, which isn't much more than you are spending on CT, but you can get a nice collar.
12/15/14 at 8:13am