I do not think you will have much of a problem getting a 6.75 inch brace height bow to shoot accurately with your draw length. The distance of the powerstroke and not necessarily the time is what makes a bow somewhat more or less critical to shoot (all else being equal). There is also definitely something to be said for the bow's riser geometry as well. A bow with a short brace height and little to no reflex is going to be more accurate to shoot than one with alot of reflex. It is more of the sum of all of the bow's physical characteristics rather than just one which makes it more critical or less critical to shoot.

Hope this helps.