Lotsa questions, curiositycat! It would have been so much quicker and easier to side it with plywood, but I didn't want to spend the money. THere was a very rudimentary pieced plywood roof on the crate, but I took it down and covered the floor with it. We bought plywood for the roof, it took 3 sheets. The only plywood we had laying around, I used to build the human door (and it was pretty thin stuff.)
The crate top is almost exactly 5.5 feet tall (I can just walk through without hitting my head, lol). The peaked roof adds another 1.5 feet. Hopefully it will be easy to clean out. I wish it were wider, less than 4 feet. Putting two of those together would have been awesome! Could you stack your shorter pallets to get more height and reinforce them together?
A couple people have commented on the rocks, I really really like that part too. It made a huge difference in cuteness factor!