At 2a 2a the market window is 50% - 67.7%. If there is no roll that immediately loses your opponent's market then cubing is correct and it could be non-optionally correct if you yourself have a market loser.
Here is one (assuming optimal play) with not cubing being a huge blunder and you have less than 44% win chance. If you don't cube here your opponent will cube you in next roll if he his not hit. Thus, there is no downside at all to cubing now and of course you want the cube on 2 for the times you hit.
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| XGID=-BBBBBB----Aa-b--b-bBbbbb-:0:0:1:00:0:0:0:2:10 | |||||
| Blue on roll, cube action? | |||||
| Analyzed in XG Roller++ | No double | Double/Take |
| Player Winning Chances: | 43.95% (G:5.35% B:0.03%) | 44.12% (G:4.46% B:0.02%) |
| Opponent Winning Chances: | 56.05% (G:1.41% B:0.01%) | 55.88% (G:1.41% B:0.01%) |
| Cubeless Equities | -0.049 | -0.331 |
| Cubeful Equities | ||
| No double: | -0.504 (-0.172) | |
| Double/Take: | -0.331 | |
| Double/Pass: | +1.000 (+1.331) | |
| Best Cube action: Double / Take | ||
eXtreme Gammon Version: 2.10, MET: Kazaross XG2
When losing 3a 2a your doubling window is 58.4% - 73.8%. The opponent's doubling window may be surprisingly low 41.6% - 63.2%. Remember though that the calculation assumes the cube is dead from then on. If the automatic recube is taken into account the window is instead 66.7% - 75.1%. If the cube reaches 2 though the cube is dead and there is no cube power at all.
In the following position you are under 48% but not doubling is a blunder. Similar reasoning as the previous position applies. If you roll 21 this turn your opponent will have a big cash and you significantly regret your cube. On most of your misses though it is a very small drop. The regret you have from having to play the game out on 2 instead of dropping for 1 is very small. Compare that to the big regrets you would have from not cubing on the 8 rolls which bear you off.
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| XGID=----A-A--------------a-a--:0:0:1:00:0:1:0:3:10 | |||||
| Blue on roll, cube action? | |||||
| Analyzed in XG Roller++ | No double | Double/Take |
| Player Winning Chances: | 47.61% (G:0.00% B:0.00%) | 47.72% (G:0.00% B:0.00%) |
| Opponent Winning Chances: | 52.39% (G:0.00% B:0.00%) | 52.28% (G:0.00% B:0.00%) |
| Cubeless Equities | -0.048 | -0.410 |
| Cubeful Equities | ||
| No double: | -0.556 (-0.146) | |
| Double/Take: | -0.410 | |
| Double/Pass: | +1.000 (+1.410) | |
| Best Cube action: Double / Take | ||
eXtreme Gammon Version: 2.10, MET: Kazaross XG2