How can the effective top tube length be larger than the actual length?
Because it slopes down a little. If you measured horizontally from the front of the top tube to the seat tube, you would be on the seat tube or seatpost, above the top tube. This is a bit further away
I'm a bit irritated. How can the effective top tube length be larger than the actual length?
Also would you split the 17t EAI cog?