These pay now/pay later problems rely heavily not only on the amount of immediate shots left but also on the relative timing. They can be, like this one is, very touchy. In the variant all I did was move the opponent's spare from his 2pt to his 6pt and already it's correct to pay now. The further back you move that spare the more correct it will be to pay now.
  White is Player 2
score: 0 pip: 87  Unlimited Game Jacoby Beaver  pip: 66 score: 0
Blue is Player 1  
XGID=CCCbBBBbbcbca:1:1:1:34:0:0:3:0:10 
Blue to play 34 
1.  Rollout^{1}  7/4 7/3  eq: +0.184 
 Player: Opponent:  63.05% (G:1.52% B:0.02%) 36.95% (G:3.41% B:0.08%)  Conf.: ± 0.006 (+0.179...+0.190)  [100.0%] Duration: 54.2 seconds 

2.  Rollout^{1}  11/8 11/7  eq: +0.131 (0.053) 
 Player: Opponent:  60.63% (G:0.93% B:0.00%) 39.37% (G:2.84% B:0.04%)  Conf.: ± 0.006 (+0.125...+0.137)  [0.0%] Duration: 48.1 seconds 


^{1} 648 Games rolled with Variance Reduction. Dice Seed: 11769768 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.206.prerelease
  White is Player 2
score: 0 pip: 91  Unlimited Game Jacoby Beaver  pip: 66 score: 0
Blue is Player 1  
XGID=CCCbBBBcbcbba:1:1:1:34:0:0:3:0:10 
Blue to play 34 
1.  Rollout^{1}  11/8 11/7  eq: +0.170 
 Player: Opponent:  62.31% (G:0.95% B:0.01%) 37.69% (G:3.10% B:0.05%)  Conf.: ± 0.004 (+0.166...+0.173)  [99.9%] Duration: 2 minutes 23 seconds 

2.  Rollout^{1}  7/4 7/3  eq: +0.161 (0.009) 
 Player: Opponent:  61.72% (G:0.87% B:0.01%) 38.28% (G:2.65% B:0.07%)  Conf.: ± 0.004 (+0.156...+0.165)  [0.1%] Duration: 2 minutes 18 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 11769768 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.206.prerelease