I would change the design. Take out what you have and renail together to make: 2 roosts side by side at the same height - over your pan. The roosts can be about 18" apart. That is how mine is - it is about my waist height above the floor so they can jump up on it. I also put a milk crate there for the younger ones to use as a stool.
At night, one row puts their heads between the chickens on the row in front of them to keep warm (in the winter). (My second roost bar is 12' apart at one end and 18" or so at the other end - so they can choose their distance from the second row). I can hang a heat lamp over them all at one height. There is no fighting for the highest roost. No lower roost to get pooped on.
To hold up one end, just nail a 2by4 on the wall under the window to support the two roosts - and build a support for the other end.