DISCLAIMER: This is unsupported and may cause your game to act funny...
Open your DangrousWaters.ini file and fine a line of code that says:
Then number (in this case 16) is the maximum time compression factor the sim is allowed to use, try changing it to 32. if you have a good rig
maybe try 64.
BTW 20 mins is not that long to wait in DW, I've made a mission or two where you have to conduct operations over the span of a day or more and may spend hours hunting for an enemy.