If you haven't had the board flashed for the lower settings then it is 'possible' to get to 12 bps but fiddly. Set the board to 14 bps then exit the setup mode. Go back in and increase the bolt delay and loader delay. You may have to set these to the max delay and then still increase the dwell to slow it down enough !
Last time I tried this, just using the bolt delay setting on max took it down to 13 bps.