Position A
  White is Player 2
score: 0 pip: 146  13 point match  pip: 112 score: 0
Blue is Player 1   XGID=BBBbCBdBcBdb:0:0:1:42:0:0:0:13:10  Blue to play 42 
1.  Rollout^{1}  18/16 18/14  eq: +0,309   Player: Opponent:  59,03% (G:10,83% B:0,23%) 40,97% (G:8,76% B:0,26%)  Conf.: ± 0,008 (+0,302...+0,317)  [100,0%] Duration: 40 minutes 25 seconds 
 2.  Rollout^{1}  13/7  eq: +0,228 (0,081)   Player: Opponent:  56,98% (G:11,26% B:0,21%) 43,02% (G:8,30% B:0,32%)  Conf.: ± 0,008 (+0,221...+0,236)  [0,0%] Duration: 37 minutes 25 seconds 
 3.  Rollout^{1}  8/6 8/4  eq: +0,216 (0,093)   Player: Opponent:  56,35% (G:11,26% B:0,21%) 43,65% (G:8,47% B:0,29%)  Conf.: ± 0,009 (+0,207...+0,225)  [0,0%] Duration: 38 minutes 21 seconds 
 4.  Rollout^{1}  6/2 4/2  eq: +0,205 (0,104)   Player: Opponent:  56,51% (G:10,97% B:0,19%) 43,49% (G:9,37% B:0,33%)  Conf.: ± 0,008 (+0,197...+0,213)  [0,0%] Duration: 37 minutes 30 seconds 
 5.  Rollout^{1}  13/11 13/9  eq: +0,164 (0,145)   Player: Opponent:  55,29% (G:10,91% B:0,18%) 44,71% (G:8,03% B:0,29%)  Conf.: ± 0,008 (+0,156...+0,172)  [0,0%] Duration: 21 minutes 26 seconds 
  ^{1} 2592 Games rolled with Variance Reduction. Moves: 3ply, cube decisions: XG Roller

This is an original position that I've came across during a match. Not spending much time for thinking this through, I've made 6/2 4/2, which looked automatic to me at the time. I rejected any 18 or 13point running play since it exposed two blots, and 8/6 8/4 because I liked leaving some safe sixes. The 8point guys give some timing in case I want to hold the anchors for 1 more roll. Puzzles fell quickly into place, and a quick decision was made.
Far from it. The position is actually much more straightforward. We got big board. He's got only 2pt. board with not many builders. We are way ahead in the race. So race. 13/11 13/9 disconnects our main racing liabilty  the farthest anchor. 13/7  a bit better, but also risks disconnecting. Just go with straightforward 18/16 18/14, which clears the biggest liability, while the risk is still low. 
Position B
  White is Player 2
score: 0 pip: 142  13 point match  pip: 112 score: 0
Blue is Player 1   XGID=BBBcCBcBbBbbba:0:0:1:42:0:0:0:13:10  Blue to play 42 
1.  Rollout^{1}  8/6 8/4  eq: +0,348   Player: Opponent:  59,69% (G:13,98% B:0,30%) 40,31% (G:8,37% B:0,23%)  Conf.: ± 0,008 (+0,340...+0,356)  [56,3%] Duration: 21 minutes 34 seconds 
 2.  Rollout^{1}  6/2 4/2  eq: +0,347 (0,001)   Player: Opponent:  59,65% (G:14,91% B:0,28%) 40,35% (G:9,74% B:0,28%)  Conf.: ± 0,009 (+0,339...+0,356)  [43,7%] Duration: 21 minutes 33 seconds 
 3.  Rollout^{1}  18/16 18/14  eq: +0,293 (0,055)   Player: Opponent:  58,08% (G:15,91% B:0,44%) 41,92% (G:12,27% B:0,28%)  Conf.: ± 0,008 (+0,285...+0,301)  [0,0%] Duration: 22 minutes 53 seconds 
 4.  Rollout^{1}  13/7  eq: +0,232 (0,116)   Player: Opponent:  56,23% (G:17,01% B:0,36%) 43,77% (G:11,92% B:0,38%)  Conf.: ± 0,008 (+0,224...+0,241)  [0,0%] Duration: 22 minutes 15 seconds 
 5.  Rollout^{1}  13/11 13/9  eq: +0,177 (0,171)   Player: Opponent:  54,82% (G:16,71% B:0,45%) 45,18% (G:12,89% B:0,38%)  Conf.: ± 0,010 (+0,167...+0,187)  [0,0%] Duration: 21 minutes 12 seconds 
  ^{1} 2592 Games rolled with Variance Reduction. Moves: 3ply, cube decisions: XG Roller

I've played around with some variants and quickly figured that the opp's 3point board is flipping the play. Even with a blot without direct covers, as in position B, such board is enough to make the doubleblotting running plays too risky. Hadn't that blot been there, the running plays would've been much bigger blunders. 
Position C
  White is Player 2
score: 0 pip: 138  13 point match  pip: 112 score: 0
Blue is Player 1   XGID=BBBbCBcBcBdab:0:0:1:42:0:0:0:13:10  Blue to play 42 
1.  Rollout^{1}  13/7  eq: +0,115   Player: Opponent:  54,08% (G:11,90% B:0,23%) 45,92% (G:10,35% B:0,41%)  Conf.: ± 0,008 (+0,107...+0,122)  [81,2%] Duration: 18 minutes 10 seconds 
 2.  Rollout^{1}  18/16 18/14  eq: +0,110 (0,005)   Player: Opponent:  54,29% (G:10,42% B:0,31%) 45,71% (G:11,80% B:0,34%)  Conf.: ± 0,008 (+0,102...+0,118)  [18,8%] Duration: 19 minutes 51 seconds 
 3.  Rollout^{1}  6/2 4/2  eq: +0,067 (0,048)   Player: Opponent:  53,05% (G:9,00% B:0,18%) 46,95% (G:10,60% B:0,36%)  Conf.: ± 0,008 (+0,059...+0,075)  [0,0%] Duration: 18 minutes 15 seconds 
 4.  Rollout^{1}  8/6 8/4  eq: +0,060 (0,055)   Player: Opponent:  52,71% (G:9,00% B:0,19%) 47,29% (G:9,86% B:0,29%)  Conf.: ± 0,008 (+0,052...+0,068)  [0,0%] Duration: 17 minutes 16 seconds 
 5.  Rollout^{1}  13/11 13/9  eq: +0,059 (0,056)   Player: Opponent:  52,10% (G:13,24% B:0,25%) 47,90% (G:10,72% B:0,39%)  Conf.: ± 0,008 (+0,051...+0,066)  [0,0%] Duration: 16 minutes 17 seconds 
  ^{1} 2592 Games rolled with Variance Reduction. Moves: 3ply, cube decisions: XG Roller

Opp has 2point board? Just race. Opp most likely is going to strengthen his position next roll, so the risk of running will be increasing with time. Although this time the blot on his 20pt. makes 13/7 a contender. After 18/16 18/14 opp has 12 hit&covers (21 22 23 26 41 43 44), with 22 and 44 being the crushers. 13/7 gives some shots too, but those are much less risky, and if we are missed we have bought ourselves some time to roll doubles for the rear guys. 
Position D
  White is Player 2
score: 0 pip: 142  13 point match  pip: 112 score: 0
Blue is Player 1   XGID=BBBbCBcBabBcca:0:0:1:42:0:0:0:13:10  Blue to play 42 
1.  Rollout^{1}  13/7  eq: +0,050   Player: Opponent:  52,57% (G:11,19% B:0,22%) 47,43% (G:11,11% B:0,44%)  Conf.: ± 0,008 (+0,042...+0,057)  [100,0%] Duration: 18 minutes 47 seconds 
 2.  Rollout^{1}  13/11 13/9  eq: +0,023 (0,027)   Player: Opponent:  51,31% (G:12,75% B:0,38%) 48,69% (G:10,97% B:0,38%)  Conf.: ± 0,007 (+0,015...+0,030)  [0,0%] Duration: 17 minutes 35 seconds 
 3.  Rollout^{1}  6/2 4/2  eq: +0,006 (0,044)   Player: Opponent:  51,30% (G:10,04% B:0,17%) 48,70% (G:12,16% B:0,45%)  Conf.: ± 0,008 (0,002...+0,014)  [0,0%] Duration: 19 minutes 04 seconds 
 4.  Rollout^{1}  8/6 8/4  eq: 0,000 (0,050)   Player: Opponent:  50,89% (G:9,63% B:0,17%) 49,11% (G:10,91% B:0,36%)  Conf.: ± 0,008 (0,008...+0,008)  [0,0%] Duration: 18 minutes 16 seconds 
 5.  Rollout^{1}  18/16 18/14  eq: 0,127 (0,177)   Player: Opponent:  47,56% (G:11,17% B:0,28%) 52,44% (G:13,84% B:0,41%)  Conf.: ± 0,007 (0,135...0,120)  [0,0%] Duration: 19 minutes 49 seconds 
  ^{1} 2592 Games rolled with Variance Reduction. Moves: 3ply, cube decisions: XG Roller

The same principle as in the previous position applies here. Break before opp's board will get even stronger. 18/16 18/14 becomes much too risky though. 11 12 14 15 22 24 26 44 45 46 all hit and cover for the total of 17 rolls. Out of those only 22 stands out as a quadruple crusher, but other rolls are also much stronger than the hit&covers from position C.
So it's correct to break the 13 point to buy some time. Better way to do this is 13/7 rather than 13/19 13/11. Looking at the dice distribution (opp's next roll, 4ply analysis, equity is shown for our side), generally it's similar, but few rolls are making the main swing. After 13/7, there are 2 positive peaks better than the rest of the field, while after 13/11 13/9 those peaks are gone, and in their place, a negative peak comes up in the form of a 22 joker. 