Anth this is a great review - and while not surprising considering with whom you're working, is still very valuable to the forum. Before I engineer another pond, Otto will be on site consulting - it will be a cost I build in for the client that simply isn't negotiable. If a client wants to cut corners and take risks to save money, it's not a project in which I'm interested. Thankfully I have a day job that pays the bills, and can afford to walk away from projects.