Time for a Redshiftt update. The 6-relay/receiver control box design is nearly final, so here’s a rendering from Solidworks:
Overall size is about 9 x 5 x 1 5/8″. The base is stainless steel, while the cover is transparent red vacuum-formed polycarbonate for radio transparency, plus it lets the user see the LED indicator lights inside to confirm power and the state of each relay. If the user wants to use fuses that light up when the fuse blows, they would be visible too, for quick diagnostics. All six SPDT relays and the internal wiring are good for 30 Amps per relay.
By swinging the edge clasps out, the cover lifts off as above. There are 6 ATO/ATC fuse holders, and 12 paired lugs for wiring connections, six will be pre-wired as a fused circuit to the common pole of each relay. The user can then wire their own individual circuits to the normally open or normally closed pole, depending on how they want each circuit to behave. Wire entry is anywhere along each long edge for maximum flexibility, when the cover goes back on the exiting wires are clamped between strips of foam rubber which form around the wires when the edge clasps draw the cover down. That and embedded seals that compress against the endwalls of the metal base will make the enclosure weatherproof.
So all that’s left to do is designing some brackets to allow mounting options without increasing the footprint.