Great coop!...I would lay the roost boards flat...easier on the feet (and balance) for the hens at night. Also makes a good place to dribble powdered pest control ( for lice) and DE.
And I agree with some of the other suggestions; especially about putting a little ring or something on the pop door latch so it can't be opened by a predator.
I have the same type of latch and I simply put one of my daughter's key chain rings on the hole of the latch to keep it from opening.