Hmmmm. Six RIRs in 16 square feet. Generally 24 square feet would be recommended as a minimum, but I think you setup is OK as long as you birds have adequate roosting space and can get outside when they want. What I like is that you have several roosting bars spaced apart from each other. So if...
It's not perfect, but it's not bad at all really. But I think only for night/sleeping arrangements. This is not for long term confinement.
I would use 2x4's not 2x6's for roosts, to prevent hens from roosting lengthwise on the board and piling poop on the board itself.
I think they can duck...