Brettski, I hear you, completely. Been there, done it many times. Sounds like you have done mucho homework, and are dealing with fair and honest people. Keep in mind, though, they are still spending your hard earned dollars, not theirs.
I still see a red flag with your project. And, without a firm understanding of your goals, I may be off base a bit.
"Pretty" doesn't count under water. Most earthmovers take pride in ponds which look like Jessica Simpson's skin...smooth. Smooth, to a fish, is like the Sahara desert. Eliminating all the trees, collecting all the roots, burying the stumps, to me, is partly unnecessary. My next word of caution to you is to pay attention to "pretty" and avoid it below the water line. That's one of those things which can push the costs way above the pain threshold.
Pour your concern to making sure the lake is built as nice as the dam. I hear your comments about projecting hard costs to finish. While that's important, you must be the guy to define "finish." If you get to the end of the money and your vision doesn't match the contractor's vision, you will have a conflict. I have seen it over and over. Look at the dam as following a blueprint, but creating the lake as art. Your interpretation of art must match the artists ability to put in on the canvas you will call your lake. It will be a shame if you have to decide the painting is finished because you ran out of paint.
