As far as "all the other brands produced," I can't say anything. I haven't ridden them all. I have a full 531 db Woodrup, and it is cushy and flexy. Maybe it's just what thin-wall 531 does.[/QUOTE]

You are right on the numbers there. Before I bought my TREK 500 in 1985 I had a Follis which was all 531 DB and I chose to go with the 501DB with cromo forks and stays just to eliminate the flex (I'm 6', lift weights and vary from 215-230# annually.) I felt so much flex with the 531 frame that I thought I was losing efficiency at high speed.