Ian,
First, thanks for doing this for the community.

I'm looking at PRsix2 bike. Below are my rough measurements from my 2014 Trek SC medium. Overall, I'm pretty with my fit but could get a little more aggressive. I also, currently ride 170mm cranks. I am around 170cm tall with about 81-82cm inseam If I mis-measured something, please let me know.

saddle setback: -35mm
Pad Y: 410mm (measured from BB center to back of pad)
Pad X: 620mm (measured from BB center to top of pad)
Saddle height: 747mm (measured from BB center straight up vertically to top of saddle.)


Looking at the chart, I could fit on a 50 or 52. I would like to know the pros/cons of either from your perspective.

Thanks