Just thinking that #6 looks very promising. With that much watershed you have to remember that your 100 year control can get pricey. Taller dam means big emergency overflow, large drain pipe or siphon. Just something to consider which property #5 has already paid for.
What about the possibility of 2x 1 acre or more ponds? Do something different in each. Looks like #6 has that possibility, which for me is more compelling than one large pond.
