I want order the CrossCurrent S2 bike today and I’m not sure what frame size to select. Looking at their chart, it seems that there is overlapping recommendations in relation to height and frame size. I am 5’10” and I weigh 170 pounds. I’m 64 years old in decent shape but I do suffer with a bad lower back. When riding, I like the seat post adjusted rather high allowing slight bend in my knees at the bottom of my pedal stroke. Gut feeling says I should order a medium frame to make it easy to get on and off the bike. Juiced frame sizing chart does suggest the option of medium or large for my height. Can someone give me guidance in this selection. Thank you!