Never needed it. I've done dozens, most of 'em all the way out to 135 from 126 or so.

Some folks say you should put a clamp there while you're spreading the frame, and I used to do this, until once I was spreading a frame and the clamp fell off! I was horrified, but it taught me a lesson. If you need a clamp at the bridge to stop the frame coming apart, your bridge needs some work. And if the bridge isn't strong enough to withstand spreading the stays a few mm, you may want to question the quality of the brazing in the rest of the frame.