I have found the Trad. American Longbow (TAL)which also stands for Tall, when properly built (limb taper, tiller, and alignment) will shoot smoother, with greater stability, durability and have less finger pinch if you follow Rob's suggestions. I am referring to a glass bow with a riser of about 14", and minimal backset (under 3/4").
An all wood, or laminated bamboo TAL, built with a 12" riser, may have an inch shaved off the length without any adverse affect. Going shorter, may result in a bow that stacks, and eventually leads to a break-down in the lower limb (over-bending), and a loss of tiller. I have seen this happen to several all bamboo longbows that were 64-65" and rated at 27". If you are going to get an all wood TAL without glass, it is better to go with a 67"/27" than 66"/27".
IMO, there are bowyers that build a short TAL, because the customer is hard to turn down. If you want shorter, than opt for a glass hybrid, with reflex-deflex, you will be happier.