IF you use a standard JACK HOWARD 66" string, you will not have to worry about brace height. IT will automatically be correct. IF you need a new string, they are available from Charlie Lamb. Charlie can also supply the Jack Howard Feather rest.
I vnever measured my brace height but 6-3/4 sounds about right. Jack's bows have about the lowest fistmele that I have seen on any bow.