And I compliment the design too. Kick it up a notch where you can and then have fun. Surely the Finance Minister is a little flexible.
I took a crack at mortar plastering the inside of my concrete waterfall. Results were adequate, but made the sanitred a lot easier and I have no leaks. Mortar is cheap and it would be a good way to achieve the measurement of 39 1/2 when using 8" block that measures 7 3/4.
Mickey the windowman