I've just started riding my new-to-me 1987 63.5cm (ctt) Marinoni Sport Touring built with SLX tubing. (Pictures when I've finished the build to my satisfaction.) I weigh just over 180, and have to say that this is a fantastic riding bike, although I'm not a "strong rider" these days. Last weekend I came down the same 40-mph hill that induced a pretty scary shimmy on my former '76 64cm Masi (and is fine on the Rambouillet with OS tubes or Miyata 912 with standard size Tange tubes). I haven't noticed any rubbing or other evidence of significant flex, but there might be some "planing" going on uphill with the Marinoni (a good thing, according to Jan Heine) - it feels like I can ride a gear higher. That descent and every other condition feel fabulous on this bike.