Short Version of my question.
If you happen to have more than one bike and you feel they all fit you well. How do the geometries compare?
I've read you typically go smaller for cross but where does smaller come in?
Stand over? Top Tube?

Long Version:
I'm all torso and no legs.
I'm currently looking at picking up a cyclocross bike. My thought was to use the top tube length of the TT bike and stand over as a guide. But I'm guessing I've simplified things too much?

My TT Bike fits me well with the addition of a longer stem. Another size up and I wouldn't be able to stand over the top tube.
My road bike I've always had low back or hip issues with after riding. I plan on addressing this problem in a week or so. Because of this I don't feel I should use it to compare.

The trouble I've been having at many of the stores I've gone to is that I feel they are pushing me into something that they have in stock. They don't have many cyclocross bikes to begin with. So they've been offering some good deals to move them out.

Rather than drawing this out any longer. I'll wait to see what some of the feedback is before I go on.
Thanks in advance.