I am looking for a roadbike. I am about 5'6 1/2". On Trek bikes I am a 52. The sizing on Giant though is S/M/L. I road a Giant Avail Comp 1 in medium and it was very painful on my arms. They were very over extended. Today I road an avail comp 2 in small and had no issues with my arms. Is a small the right size? The LBS today said I was a small not a medium. The other LBS said the opposite. I can't find online on the giant site what the sizes are equivalent to....