Finished boxing this tonight. It shouldn't fit in a 1590B, and wouldn't without the SPST footswitch, but it "just" makes it. I don't know what it is about this pedal, but it just fits right for my playing style. The touch dynamics are great.
Maybe an enclosure shot at some stage, but it's all about the guts right?
It's my own layout from a trace by Kanengomibako:
https://github.com/kanengomibako/Minerva/blob/main/Vivie_MINERVA_v1_schematic.png