So, I removed my 5600 FD and found a 349 stamped on the inside of the clamp. I purchased a 6700 FD in 34.9 size and it too has the 349 stamped inside the clamp. But the clamp fixing bolt is so tight on the down tube that it just barely fits at all. I can "just" get the bolt started but even just started the FD won't move up or down or left or right with out a rubber mallet hit.
The fixing bolt on the old 5600 FD was the exact same size and it doesn't have this issue. I guess the newer clamp is thicker metal and that is preventing the bolt from reaching far enough to make this work better.
I do have it working and the FD works great, but really, there needs to be a longer clamp bolt.