so let me get this straight.

You can only brace it to 7.5"es but yet it shoots well? If so DONT move a thing! I love to tinker but there comes a point when it aint gonna get any better without some drastic changes.

If you were over the 9" mark I'd be worried, under is fine as long as you dont whack your wrist/forearm, arrow flight is nothing short of perfect and they are going where you want them, leave it be!!!!

Use a 36" ruler to measure you string, works fine.

Also realize b50 will never stop stretching/creeping (I can never keep them straight). One is recoverable, one is not. If you dont watch it, b50/500 will drop your brace quite a bit. With the modern stuff ie dynaflight specifically I find eventually the string stops, however if you unstring it and let it sit for awhile that string wont be the same as before you unstrung it. String it back up, leave it sit for a few days strung (you can shoot if ya like), then unstring it, leave it sit for awhile and restring it, you'll see the brace heigth change however its much smaller then with b50/500.