Took it for a ride as is with my GPS. Comfortable cruising speed for me on this bike is 8mph all day long. Stepping it up to 10mph; not as pleasant pedaling experience. 12mph takes a lot more effort(faster pedaling more so then resistance). At 18mph I'm spinning the pedals. I can't break 20mph. Maybe I could with a stand up full on sprint; but I'm looking for constant cruising speed.

I wonder if this 15t cog would allow me to maintain 12mph as comfortably as 8mph is for me now?

I have about 1/2" of the dropout left. Will this 15t cog require me to remove links from the chain?