Quote Originally Posted by salsabike View Post
I know I need to go with WSD because a bike fit by a PT says I need a 50.5-51.5 top tube, no longer.
That top tube length does not lock you into WSD. I'm also a 51.5cm max and rode at least 7 bikes when I was test riding...1 was WSD. I by no means exhausted my options (non-WSD and WSD alike).

A WSD bike may or may not be the best fit for you, but it's not necessarily a requirement just because of the top tube length you mention.