my LBS suggested this, and I tried it. They put 26/39/50 FSA rings on my Ultegra cranks. That is the only brand I know of that will work. Even with them there is a ramp that needs to be ground off.
But work they do. I love it. I have 26/34 for my low gear now. But I spend
most of my time in the middle ring. With a low of 39/34 there are few places where
I need lower or higher than what the middle ring provides.
Very cool. I also put on some Shimano a520 touring pedals, and they are just dandy so far.