The solid model became slightly taller than before, due to a serious tangle of wiring below the board, with a narrower flange that fits just as well in the benchtop gripper:
Tidy brass inserts epoxied in the corners replace the previous raw screw holes in the plastic:
The screws standing on their heads have washers epoxied in place, although that’s certainly not necessary; the dab of left-over epoxy called out for something. The screws got cut down to 7 mm after curing.
The preamp attaches to a lumpy circle of loop antenna hung from the rafters and returns reasonable results:
The OpenSCAD source code as a GitHub Gist: