I'm 4'11" with short arms and I've been playing a traditional Oscar Schmidt since the 1970s. I've tried newer models, returning them to the store because the sound is "tinny". But to the problem of short arms...my left arm also bruises after not playing for a time, but then stops bothering me after I take it up again. I truly believe it's just like playing other stringed instruments...you have to develop a "callus" wherever pressure is applied. My advice is play more!