jamesdak 

Trying to get a tad more aft positioning at of Velo Orange saddle. The rails move in slightly stopping me from getting the saddle far enough aft. Anyone every successfully spread/bend rails a bit to allow more positioning.

The saddle is being used on a 2011 Trek 5.9 frame and I'm limited (as best I can tell) with using the Trek seat cap with only 20mm of rear offset.

thanks

AEO

nope, you can't do that.
at least not unless you want to split the saddle in half.

the only way to do it is to get a seatpost that has more setback to start with.
The two cheaper ones are kalloy UNO w/ 30mm offset or VO grand cru w/ 32mm offset.

FBinNY 

You can't spread the rails, but if you only need a little bit more travel, you might be able to file away from the inside of the seatpost clamp at the front. This will allow the saddle to slide back a bit farther with the narrow section in the area you've opened up.

The first generation Campagnolo seatposts (late 60s) had this feature. The saddle rail support had a semi-circular grove, but the inner wall was cut back about 10mm, so it still held top and bottom, but not to the inside.

jamesdak 

The problem is that this is a seat mast/cap setup. Does not take a standard seat post. The saddle mounts to the mast caps which fits over the mast. Don't think filing away part of a carbon fiber piece would be very safe.

FBinNY 

Yes, carbon isn't as user friendly as metal. You have to look at the construction and decide. You're removing very little, only the inside lip top and bottom, so if the supports cover a decent length of rail, you'll be OK. It also depends on how the carbon is wrapped, or whether it's a carbon reinforced molded piece.

In any case the most you can gain by this method is probably 1/4" or so. Otherwise you have very few options because they probably don't make a different mast with more setback, or a setback mast head.

Last resort, see a good fitter and review your total fit and position. Possibly a different saddle and/or change in the length of the stem might be the ticket.

I'm not a total retro grouch, but I really hate that so many high end modern bikes have so little latitude for user fit adjustments. It's really bad when you have to scrap a frame to push the saddle back a bit.

Kimmo 

What, where the rails should still be parallel? On every seat I've seen, the rails bend in fairly sharply after that point...

If so, it shouldn't take much work... bit of a head-scratcher figuring out how to apply the force though. Maybe a large bolt and nut that only just fits in between, unscrewed?