Well it took WAY longer than I guessed (or hoped), but the slot cutting is complete! It took Wednesday afternoon, all day Thursday and Friday, and a little into Saturday morning... But its done and looks pretty good - though not pretty.
The process was painful, after laying it out we made kerf cuts with the circular saw, then knocked those out with a hammer and chisel, then cleaned up the slots with a router mounted on a handmade jig... Let's hope its in the right spot!!!