Go with what you feel best on. I just bought a 48cm Felt F5 (men's frame) and love it. Actually my husband is getting the 51cm Felt F5. His is actually the floor model.
I'm 5'0" and also have a hard time finding anything in my size on at a shop. Most shops would have to special order for me. I've only been able to test two bikes that were floor models. One was the base model Lexa at our old LBS in Charlotte. The other was a Dolce at a dealer in Raleigh. My old road bike is a Trek 2000 47cm men's bike. Basically what I discovered in testing the two WSD bikes is that I prefer the fit of the men's bike, but will never be able to find the small size in a floor model to test. The older bike shop is of the opinion that I'm female so I have to have a WSD, even though I'm not as comfortable on them. The new bike shop in town listened to what I was telling them. (The new bike shop sells Specialized and Felt) Basically as far as their two brands decided that I needed to either look at the Felt 5 series or the Specialized Ameria (mostly because the Allez does not come in a small enough frame size for me.)