I want to order a mercier elle but am unsure of size. i am 5'4 1/2" and my standover clearance is 31" . Think I need the 50cm but the standover is 29 1/4 for that one.. is that too small for me? anyone? I will be riding some mtn.areas(colorado) and also more level things like tour de tucson. I hope with the right fit I'll want to ride more since now i'm riding a 25 yr old schwin. any suggestions?