Hardware store didn’t have exactly the hardware I wanted (really miss the local place which closed which had a much better selection), so have ordered from the magical land at the other end of the FedEx route.
Looks like I’m going to need a couple of dust shoes since the design I hacked up isn’t adjustable to account for different lengths of endmill stickout, so I guess it’s back to Lowes to buy another extension wand or two to cut up.
Debating on trying a design which connects to the underside of an HDZ4 which would be static relative the height of the stock.