Has anyone done this on s19 models?
No and it won't be for a long while. Unless you want to have a "space heater" that even downclocked using 2000-2500W of 220V power that still requires a deafening fan from both the PSU and miner itself at your feet. This is for old gear that you aren't trying to get massive hashrates.
whats to stop someone from running a s19 at 1% fan speed with a heavy underclock? it would be much more efficient compared to an older s9 when ran at 300W or something