I own one of those FR tanks. I don't remember it being so bad back when I was using it in the 60s and 70s, but many of those old negs look pretty bad along the edges today -- maybe the fixer didn't circulate so well either. I think they made the grooves super deep to compensate for the coarse intervals in the width adjustment. At any rate, the last time I did any 4x5 (Worldwide Pinhole Photo Day 2005 & 2006) I tray developed because of this problem.
If I ever seriously go back to 4x5, I will look for some other option. I suppose one might be able to cut the ribs down and round off the edges. That would be a lot of work, and might screw up its future use for other film sizes. The fact that I own one from back when is a sure sign it was cheap -- and probably a compromised design!