I would cold set the frame. While the good colonel is right that it's only 2mm per side, I also agree with well biked that you cannot guarantee that the stays will be aligned properly. From what I've read, you really wouldn't have to align the dropouts for a 4mm set as it doesn't change the angle enough to matter. If you're spreading 10mm like I did, then aligning the drop outs becomes more necessary. Supposedly broken axles can occur.