Hey!!, don't even worry about that, only the stock firmware cares about that, vnish doesn't read the voltage stored in the EEPROM and thus you can mix and match boards all you want, I tend to believe all other custom firmware do the same, I just don't have a good experience with them, but I know vnish works.

Obviously, since you will need to disable the fans and overclock the miner, you won't be using the stock firmware either way.

Also, you have got a loose heatsink shown in this image, you have to solder it back on, I highly doubt you can get away with no-heatsink even with Immersion cooling.

Thanks for keeping this topic updated.