For what its worth. I played around too long with over spined arrows through my bow. I shoot a 45# @ 28" flatbow, its cut 1/8 off center with a skinny string. I pull 29" so I have 30" arrows. I ended up getting perfection with a 50-55# spine w/ 125 gr points. Just my scenario, yours may be different. If your only pullling 27" you will lose a good 2-3#'s off your 50# bow, which I would scale to be sure it is a true 50# before I made a purchase. I would suggest 50-55#, or get a test kit first and save some head aches.