My elbows and knees always overlap if I lean forward, even sitting on the saddle. I have a 56cm frame/565 ETT and am "about" 5'11" (meaning less than that!).

The reality is it is about 23" from my patella to ischial tuberosities, and about 14" from my elbow to the base of my thumb. Added together, it would have to be 37" from where I sit near the rear of my saddle to the handlebar position that I use for there to be no overlap. But there is always overlap because any position I use on the handlebars is less than 37" from where I sit on the saddle.