Well you are not the only person that fits the "between sizes" category so this is not uncommon. I can make a 56 and a 58 fit just right but I prefer the 56 with a longer stem. I would have thought a 50 would be fine at your height, maybe even a 52. You did say you had short arms so that could be an issue. What about switching to a handlebar with a shorter reach? I prefer a shallow drop on my bars as well and that may help you. The 48 just sounds like you're going to small.