I am 5'11, with 34-35 inch inseam. I am not sure of my arm length, but I think they are in proportion to my body. I bought a 20" men's 7.5 FX last year and it was fine for me. I test rode the 22.5" and I felt ok on it, but a bit out of control and it was definitely a challenge just to swing my leg over. I have a feeling that would be way too big for you. I don't know if this helps given how different my height is from you, but just thought I'd throw it out there. Good luck! (Can you get some kind of gift certificate for your points instead of an actual item, or cash applied to your Amex bill? Just trying to think of a way you could purchase directly from a store instead of through Amex.)