I wound up purchasing 2 saddles: Avocet O2 Air (women's model) and the Terry Beetle. The Avocet arrived first and was put on the road bike. The Terry is now on my old touring bike (used for commuting and dirt road rides).

First to answer the question about the rails- I haven't looked directly (and I've now sold the Finesse and can't), but I suspect the rails are longer (or something about the saddle makes it less important). Before giving up on the Finesse I had it shoved as far back as I could get it (I have a straight Thomson post so that wasn't that far, but it was at the limit of what I could do). With both of the 2 new saddles, I'm not at the the limit (either fore or aft).

Avocet: So far this seems to be the saddle for me. It's far lighter than any saddle I've ever ridden, but still wide enough in the rear for me. I've done one longer ride (70 miles) and it still felt good at the end. It definitely needs some more test rides of significant distance (I'll post another update at some point), but I'm really hopeful that this saddle is the one for me.

Beetle: Definitely has potential. I have yet to ride it for more than 11 miles at a time and therefore can't comment on how it holds up for distance rides. It seems quite comfy. I can say that I did commute to work, then to a group run, then home one day wearing tri-shorts (much less padding than my typical bike shorts) and it felt fine. The material used to cover it is a little different (not as slippery). Definitely worth a try as well if it seems like the profile is right.