I could have done a better (much, I had a hangover) job cleaning up burrs from widening the counter-sink on the holes to get the screws flush mounted, but otherwise I’m pretty happy with the results.  The adapter is a fairly cheap Ebay purchase (branded “Pixco” it seems perfectly sound except for the countersinking being rather shallow), so I could always do-over.  The only 1.8mm screws I could find were too long hence the coffee can lid for cutting them cleanly.  Focus tests so far seem to be spot on, lucky.  The samples are essentially (one straightened, one white-balanced) untouched from RAW.