I don't know about that particular bow, but generally speaking, longbows will brace at around 6 3/4 to 7 3/4 inches. I'd probably start at around 7 and experiment from there.
My 62" Mahaska likes 7 1/8 inches. You want to find the spot where the bow is quietest and shoots the best for you.
Lower brace height gives a bit more cast since the power stroke (distance the arrow is on the string) is longer, but there is a limit to how low you can go without slapping the snot out of your wrist.
Hope this helps.