Dave,
Glad you mentioned the check valves. I've had a nagging suspicion that I might need this because the drain height and top of the gray tank are only about 1" different. I think I might have mentioned this somewhere in the beginning. Thanks for the input about tying the rear wall to the beam. I can see that connection being important. I have some angle iron that I can cut some clips out of. Hopefully, we'll get some good days in February to work on it. Anyone have any suggestions on fiberglass repair kits? I don't need a lot of epoxy or glass, but am not real knowledgable about the process, just willing to get my hands dirty learning. I have gotten some good information on System 3 from a book that I got at the Woodcraft Store. Thanks for the input. Carey