At only 0.65” wide by 0.75” tall, the Aion Micro 3PDT Bypass is the smallest bypass wiring PCB available, only barely larger than a 3PDT stomp switch. This makes it perfect even for micro 1590A projects!
Wiring is dead simple: the pads labels match up to every 1590B Aion PCB project, so you can run the wires straight across and be done with it. Refer to the PDF documentation for a wiring diagram along with a description of each of the connections if you want to use this for non-Aion PCBs.
Note that the newer 125B-series PCBs (2018-present) include bypass boards integrated as snap-off sub-PCBs. The micro 3PDT bypass boards are not needed with them.