Some bows have a recommended brace height mark, I'm not familiar with your bow but I did find this:
http://www.archerytalk.com/vb/showthread.php?t=959983
The are talking about 7-8.5 inches between riser (end of your rail aka barrel) and the string.
If the brace height gets too low, not only will your bow shoot to a different point of impact but in worse case the string can come off the bow. Best thing to do is to keep shooting it for a while so the string stretches before you get concerned about brace height.
PS Speed does
not increase as you twist up the string, it actually decreases. That's because the power stroke becomes shorter as the length of the string is shortened.