I am ready to pull the trigger on a Specialized Allez Comp from CL. The only problem is that the frame size is 52cm. I measure my inseam to be about 30.75" (I'm 5'7") and am afraid it might be too small. Otherwise it's perfect. I don't know how to determine whether it will be good enough or not and I don't want to drop $800 on a bike that won't fit at all. Suggestions?