Twilight of the Sun King is a rules set taking a minimalist approach to game mechanics. The core of the system is the morale check. If a unit fails a morale check, a hit is scored. Most units can take 2 or 3 hits before being removed from the game. Oddly, the game designers chose the sum of 2 average dice for the random element in a morale check. I suspect they wanted a limited range of outcomes yet they wanted the middle results to be most common. Given that there are only 3 results (Pass, Fail or Destroyed), it seems to me that this could have been done in a better way.
If a morale check total is 8 or more, the unit passes. If the morale check is 7-5, the unit takes 1 hit. If the morale check is 4 or less, the unit is immediately removed from the game.
With the sum of 2 average dice, a 5 or 6 will come up 1/3 of the time. Similarly a 8 or 9 comes up 1/3 of the time. A 7 will come up about 27.78 percent of the time. The outliers (4 and 10) each come up 2.78 percent of the time. Thus, a unit passed a straight up morale check 36.11 percent (slightly ore than 1/3) of the time. They fail 63.89 (slightly less than 2/3) of the time. 2.78 percent is an automatic removal of the unit. Rolling 2D6 would be an obvious solution but there is a problem. The spread from pass 2 destruction (8 to 4) is only 4. If you roll 2D6 you would either have a spread of 6, which throws off the modifiers to morale checks, or you would have automatic destruction occur many more times that intended. A ‘4’ would occur 16.67 percent of the time which is 6 times more than intended.
Ignoring the outliers, we can generalize and say that a unit passes 1/3 of the time and fails 1/3 of the time. That neatly works on a single D6. A unit passes on a 5+ and fails on a 4-. We could say that a unit is destroyed on a 1 but that would also occur 6 times more than intended. My solution is to make a result of 0 an automatic destruction. So, using a single D6, a 5+ is a pass, a 1-4 is a fail and a 0 or less is a destruction. The observant will not that a unit will pass 2.78 percent less than before. But you should also note that a unit that has 0 or more positive modifiers cannot be automatically destroyed. That’s probably a fair trade. Also, while the spread for pass to destruction is 5 instead of 4, it will still likely not break the system.
It is clear to me that the designers of the game wanted units to fail morale checks often with only a small chance of a catastrophic failure. However, 2 average dice are not necessary for morale checks in the game. You can yield similar results with a single D6, which I hope most gamers will appreciate.