funboard to shortboard?

I'm stepping off of my fun board and getting ready to buy a shortboard. I plan on going with a channel islands flyer but i'm not sure about the length and width i should get. It is supposed to be ridden a little shorter and a little wider than your normal shortboard but i don't know what my normal shortboard length and width are. I'm 6'1 and i weigh about 200 lbs. If anyone can help me determine what the best length for me is, well, It would be greatly appreciated. Thanks in advance.