hi I'm 14 and wiegh about 80 lbs i ride a slingshot turbo diesle 6m! it works great! but before I bought it i talked to a guy named Anton at Colorado kite force he helped me find a great kite size. so go talk to some one like a kite shop. Anton also watched me fly a trainer kite first to see my skills. since he said they were good he hooked me up with a 6m. also slingshot will work with you a bit on getting a good price!
Cheers and happy new year!!!