I was wondering if some saddles had rails that let you have less setback. I know people usually would buy a non-offset post, but if you had a proprietary seat post then are there saddles with a little more leeway in terms of how far foward you can push it?

Um. I think you're asking if saddles have differing lengths of rails. The answer is yes, and I bought an Fizik Arione for this reason. Also it rocks, but I didn't find that out until after I bought it.

Perhaps explain what you mean by proprietary post...which post?
Will only provide my opinion....most have the opposite problem...they can't push their saddle back far enough.
My opinion is...choosing a saddle because of travel either fore or aft is a poor reason to choose a saddle as
it may preclude the one saddle that is actually comfortable. Generally much easier to change the post.
Perhaps explain which frame and post you use. Pushing saddles forward is typically a better scenario than aft
because the seat clamp ends up under the part of the seat that you sit on.
The Arione has long seat rails but again, I believe its the wrong criteria to choose a saddle.
Good luck.

I shudder to think that there could be a situation where you'd have to choose a saddle based on what seatpost it fits on instead of how comfortable your ass is on it.