Maybe it is just me but this really doesn't seem like a sound idea. I watched some silly tv show where they built bunk beds out of 4" PVC for kids. It wasn't very sturdy even after it had all been glued together. Would you be better off just building it out of wood? Certainly cheaper. Heck even Cabelas sells a complete tower kit (made of metal) with ladder and everything for only $299. You are going to have that much into that PVC thing before you are done. Don't get me wrong, I am not trying to bash you for your idea. I just don't think I would trust my safety to PVC. Falling doesn't hurt but hitting the ground sure does. Be safe.