You would also need to get some stacked belleville springs to compensate for the board creeping with time, making the connections go higher resistance. I would also probably derate a lot, if you are at 400v then under 5A would be fine, though I would guess what would also work would be PCB mounted 1/4in spade connectors and the male side, as this also allows for a good contact area, and will handle slight misalignment, plus it is very obviously a power connection.
If you are using the belleville springs/washers you will need 2 per side, arranged cup to cup so they have the most travel, and a brass washer between the standoff and the board, and another on the top by the springs, to spread the load out to a larger board area, or a third beleville spring with cup towards the board. The bellevile springs are nice, compact and very constant in pressure, and in M3 should be reasonably heap, though a lot more than a simple punched washer.