I have a '91 62cm RBT and agree it feels more sprite than my Rivendells,
maybe with the exception of the 64cm Quickbeam. I attribute the RBT's
liveliness to standard diameter tubing (1" TT, 1 1/8" DT), since I have the
same feeling on any the bikes I've owned or still own from the 80's when
I had a 1992 50cm RB-T that was too small for me, no matter what I did to
it. It was my first Bridgestone. It felt neither lively, nor spritely.
But for some reason, this 56cm RB-T (same year) most definitely feels
supple. I haven't ridden enough to know if it's planing or not, but my
