Thanks guys - hearing your view is reassurance that I won't go out and spend the money and regret not asking around first. My contractor may be helpful on the costs and did prescribe the sheeps foot roller and a foot thick minimum on the clay layer. He also said I'd need to have a water well ahead of time so we can put a layer of water on the new clay liner immediately to keep it from cracking and leaking.

I'm thinking if I can invent a lake sealant I might save people a lot of money and make some along the way. Seems those silica gel animals that grow to 20 times their size could be dumped down and would slide into the low cracks and expand - although not sure how long they'd last!