Top rail is going to be 2"x6" with the 4xs length 6' - 5' - 6' = 17' total length of run. I will have a human door, I may just make the human door bigger to accommodate a wheel barrow. it'll be framed out in the 5' section with 1' on each side and a 3' wide door. My rafters will be 2x4s and I plan on a slant roof. However I will discuss with the wife tonight, You may be right about the head clearance as now that I'm really mulling it over if I was to get 4 10' and make the front slant 7' and the back 6' that would ensure plenty of space. That was the original plan was a slant roof, I am thinking about this and I think raising the front to 7' would give me plenty of head room and offer a decent slant. the roof will be 75% down the entire run and will be corrugated metal. I am leaving the last 25% open because the run is north facing with a 6' privacy fence behind, which will keep the chicken cool in the summer however allows very little direct light in the run. To prevent a damp run (even with good drainage) I'm leaving the last 25% to allow for 1-3 hours of afternoon sunlight to keep the run nice and dry and allow the girls on a cool day to warm themselves. they will of course still get sun light through the day as it will filter in through the back some, but not enough to keep the run dry.