Designing Path Racer/Porteur Frame - opinions?

It's just my personal opinion and feel of the material from riding them. To me, 531 feels stiff, springy, strong. CrMo feels strong but lacks the same give and take "springy" feel I get from 531.

I realize that's very vague and inarticulate, those are just the feelings that come to mind for me.

Cheers

You just described a butted steel frame.

you might not like plain gauge 531 though.