If i didnt already have a nice regulation doublet, I would probably get myself a sheriffmuir. The regulation doublet is a lot like a sheriffmuir but with lapells and three buttons up the side, but with the same flaps at the bottom and same cuffs. You've got more versitility with waistcoat choice with a sheriffmuir (as outlined above) than a regulation doublet mostly because a regulation doublet should usually be worn with a 3 button waistcoat , but not usually a five button waist coat. At least if you go by 'dressing tradition' =)