I am 5'9" with average body ratios. The bike does not seem to be too small but I do think that a 54 cm would be a better fit. I would think that if it is too small I would not be tending to slide forward but maybe I am wrong.

It was suggested that I may have poor posture since I some lower back problem but not major so that will probably not improve. My back problems are not new. I have delt with them since a teenager. I am an old fart now.

I want to thank all for thier thoughts.