Originally Posted by Doug Fattic

Those dimensions are solid except for the seat tube angle. If you are going to use North Road handlebars (the shape of a handlebar on old English 3 speeds or Chicago era Schwinns), a 72.5º ST angle won't work well. If you are going to use MTB style of handlebars with maybe a 6º bend, your bicycle position is more forward and a steeper seat tube angle is okay. The problem is that a person sits more upright with north road handlebars and what is happening is that their body is being pivoted backward. This means the saddle has to also be placed rearward. The Dutch - who ride this kind of bicycle with north road handlebars all the time - have even slacker angles than 71º. I studied their frame designs when I was designing our Ukraine bikes to see what they have successfully done.

If you were to make 2 identical bicycles with north road handlebars, except one with a 72.5 ST angle and the other with a 71º, it would quickly become obvious to you which is the superior design. You wouldn't go 100 meters before wishing you saddle could go further back on the model with the steeper angle. The student that made the frame in my pictures based his design on the position he found most comfortable on a fitting bike. With a 25mm setback seat post, he found that a 70º seat angle worked well for him. if you were to put your chosen handlebars and saddle on a fitting bike you would discover the same thing too. Not necessarily that 70º is perfect but that it would be at least 71º and maybe less.

And now a word about handlebar shapes. The typical MTB bar is designed for riding fast downhill trying to avoid injury and death. It is a more forward position. Swept back handlebars are designed to ride comfortably at a walking effort so one doesn't arrive at their destination all sweaty and gasping for air. I found this shape to be more comfortable for a city cruiser. Again I assumed the Dutch (that ride everywhere on their bicycles) know what works best for the kind of riding they do.