Are you going to have an enclosed run attached to the house? I find it hard to believe that you guys don't have hawks and eagles up there? What about raccoons? That's awesome how you have used recycled materials wherever possible! I'm building one now and I just topped $500 on the project, I don't have materials laying around nor do I have the time to hunt Craig's list so it is what it is. Someone else on here mentioned the vinyl floor tiles, a must have on my list. Water flies right off of that surface and it will help protect your untreated slats especially if you throw down some cement board first. I needed to cover around 20 sq. ft. with my vinyl and spent $4.50 at Lowes on it. Good job!