Thanks again, Scooper! This is what I meant. I knew there was variation in wall thickness, and in my opinion there's a noticeably more lively performance/feel. Years ago when I knew jack about tube specs I much preferred the higher-end full-531 Trek I had vs. what I found out later was a main-triangle-only 531 frame; it was all in the rhythm between myself and the bike. I'm certainly open to non-531, as long as the quality is there, and for my tastes, straight gauge is of a lesser quality, performancewise.