Will be interested to see if the 17" works with the 3" height...I think the closer to the board the roost is the narrower the board can be.Thanks for the great idea! coop is built, roosts and trays are up, loving the clean up! my roosts are approx 3 inches above the poop trays (due to room, the one at the back is about 3" from the bottom of the tray, the one on the right is I think 3.5 or 4 inches off) and my boards are 17 and 20 inches wide. We'll see how well the 17 inch one works (the one on the side), that one we may have to make bigger, but my husband didn't want to buy another sheet of plywood, I told him we could try it and see if it works ok, if not, we'll be buying another sheet of plywood. (so far so good though) the roost at the back is about 20 inches off the ground. I blocked off the nesting boxes as it will be awhile yet. Here 3 the girls are on the edge of the poop tray, but they settle on the roost at night. They were fighting over the lower roost, now they fight over the upper one :/ Thank you for this thread and idea!