26 foot span? Can you have a post in the middle and make it 2 13 foot spans?
Liabilty will keep anyone who really knows from saying anything. The rest of us would just be guessing.
The slope of your roof, wind load and/or snow load for your location all would make a huge difference.
Any of your friends have a building with a 26 or 28 foot side door on a sidewall, copy what they have?
That's a pertty good span.