one of my B17s is narrower than the others, but is still very comfortable for me, but I'm a narrow guy. I still think someone can sort of get a rough idea of how a bike will work, especially if you can compare it to a seat that you know works, but its still going to be a bit of hit and miss.
And also, lets face it, its hard, if not impossible to factor out or in the "princess and the pea" aspect of how something can work out or not for an individual.
Another narrow rider here. A normal B17 is too wide for me. My Selle Anatomica is almost too wide. But the hammock effect makes it doable. I bought it, used to try out, and probably won't buy another, due to the width. My perfect saddle is a B17 Narrow. I also don't use chamois, or any padding. I'm currently riding my C15 until the end of the rainy season. I realize I've strayed somewhat off topic here. Carry on