Not answering your questions, but an interesting result here. If you go through the math of calculating White's cube efficiency for owning the 4-cube here you find that it's higher than 80%. Note that, according to the rollout, if White accepts he wins 22.27% of games and that the take is corrcect by ~0.04 emg units. Thus he could be even (admittedly slightly) worse than 22.27% and still have a correct take. Further, based upon the gammon breakdown numbers of the take part of the rollout and using the R-K MET, White's worthless cube takepoint corresponds to 32.0% total wins and a perfectly efficient cube (drop/take line when going 4-->8) corresponds to 20.7% total wins. The actual takepoint (accounting for recube vig) is below 22.27% wins and (32.0 - 22.7)/(32.0 - 20.7) > 80%.
To see if the gammon win fraction for Blue was reasonable, I ran this as an unlimited=$-game session. That result is below. The gammons (and gammon win fraction) are close enough to your matchscore rollout results that I find them believable.
One last note: A month or so ago in response to MCG (I believe), I mentioned that for late matchscores the cube efficiency is not well understood. About a year ago I saw a position (here?) which was similarly late in the match, with a matchscore deficit, where the recube vig was in the 40's. I recall discussing this with JOH (possibly in Madison in September). From these two (one apocryphal) examples, my reply to MCG seems confirmed. Lot of uncharted ground out there....
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| XGID=baBBBBBA---A-A----bbbbbBb-:1:1:1:D:0:0:0:0:10 | |||||
| Blue double to 4 take ? | |||||
| Analyzed in Rollout | |
| No Double | |
| Player Winning Chances: | 77.72% (G: 39.52% B: 2.68%) |
| Opponent Winning Chances: | 22.28% (G: 3.79% B: 0.14%) |
| Double/Take | |
| Player Winning Chances: | 77.67% (G: 40.71% B: 2.68%) |
| Opponent Winning Chances: | 22.33% (G: 4.15% B: 0.15%) |
| Cubeless Equities | |
| No Redouble: | +0.937 |
| Redouble: | +1.889 |
| Cubeful Equities | |
| No Redouble: | +1.115 |
| Redouble/Take: | +1.703 (+0.588) |
| Redouble/Drop: | +1.000 (-0.115) |
| Best Cube action: Too Good to Redouble / Drop | |
| Rollout details | |
| 1296 Games rolled with Variance Reduction. Dice Seed: 3246638 Moves and cube decisions: 3 ply | |
| Confidence No Redouble: | ± 0.010 (+1.105...+1.125) |
| Confidence Redouble: | ± 0.023 (+1.680...+1.726) |
| Double Decision confidence: | 100.0% |
| Take Decision confidence: | 100.0% |
| Duration: 8 minutes 05 seconds | |
eXtreme Gammon Version: 1.21