IMO, 126mm to 135mm is too much. In addition to respacing, you need to think about the dropouts. They will have to be bent back inwards. In a stock frame the rear dropouts are parallel to eachother. When you respace the stays, they are no longer parallal. A 4mm respace really doesn't do too much. A 9mm could give you some problems. Sheldon Brown explains it somewhere on the site.
Tim
I agree that the dropout alignment is a concern when you change the dropout spacing as much as 9mm. But that's one reason the OP should have gone ahead and cold set the frame all the way to 135mm and not just to 130mm, because then he could have the dropouts re-aligned, which is not a big deal. Also, if the dropouts are stamped and not forged, they're usually flexible enough that they "self-align" to a great degree when the QR or axle nut is secured nice and tight, so it might not matter anyway-