Deciding whether you gain by doubling requires what pro-betters call a Risk/Gain analysis. For this you need to divide what you risk by your risk plus what you stand to gain. Eh? What does that mean. The situation here is that we lead 4-away, 5-away and we hold the 2 cube. We can see what we stand to gain and to lose as follows.
(a)No double/win, we lead 3-0, MWC (match winning chances)75%
(b)Double/win we win the match, MWC 100%
(c)No double/lose, we trail 1-2, MWC 43%
(d)Double/lose, we lose the match, MWC 0%
Our risk is the difference between c & d, 43% is what we stand to lose.
Our gain is the difference between a and b, 25% is what we stand to gain.
Risk/Risk + Gain = 43/68 or 63%. This is what we need as a minimum in order to turn the cube.
You get very slightly different results with different ME tables, but the principle remains the same. There is also some degree of simplification here. In line a for example, I have ignored the fact that we may double later.
We could just use Woolsey's rule of course. Are you absolutely sure that this is a take? Some of us are, but I'm not! I think it probably is, but I wouldn't be surprised to be wrong. Flattish full board bearoffs, which this is just about to become, favour the leader by a bit more than the pipcount, having some characteristics of pip races and some of roll races. Pip/roll hybrids as they are known are notoriously tough for the trailer when he can't use the cube.
QuoteMy take is that a market losing sequence is just as likely as a game-losing sequence. Most sequences will preserve the status quo (or as the race goes on accrue advantage to us, all other things being equal.) so we'll probably still have a cube next roll. This tells me that rolling is probably not a very big cube error even if it's technically correct to cube now.
There are no game losing sequences, as we can't be doubled out. Certainly we will usually have a double next turn, but often we won't get a take. If we were only just in the window, we wouldn't lose much by waiting, but here we are a lot better than our minimum.
Look at it another way. In money play, redoubling means that you lose the ability to cash (or make an efficient redouble) later, while your opponent gains the advantage that you have just given away. Here we lose later use of the cube, but the opponent doesn't gain anything like as much as usual. His auto recube only gains him one extra point rather than the normal 4.