Recapping the last several posts on reply rolls to 31P, 42P, 53P, 61P, and 64P.
*** Prime Structure ***
31, 42, and 61 are priming rolls. 31 froms the best prime, 42 second best and 61 last.
Against these, the general strategy is to split and go for an anchor before the prime gets too scary. Two down is the wrong concept since you are at a disadvantage in the priming game and slotting is too risky.
Nevertheless, slotting with 21$ is still correct against 61P.
When you have a choice of splits, Reverse splits tend to do better than normal split. I think the reason is if the opponent chooses to attack, you would rather he attack you on a less desirable point (lower on the home board and not part of a contiguous prime) - so splitting further back or the reverse split makes sense.
Against 61P you run with 62, 63, and 63 as there are no alternatives.
Against 31P and 42P splitting with 62 is clear.
64 against 31P and 42P are close.
64. You run against 31P and make a point against 42P. After 31P-64R you are slightly up in the race and according to Dmitriy also more likely to clean up the blot if missed than compared to 31P-63.
64. Make the point against 42P, though running is only a small error. Perhaps the reason is you are not really ahead in the race even if missed. On the other hand, making a point is constructive and 42P while priming isn't overwhelmingly scary just yet. Splitting as in 42P-64S is a definite mistake. I always used to play this way and will have to remember not to going forward. I guess you are just leading with the chin and asking for the dice to punish you.
63. Split against both 42P and 31P but running is not too bad. It is only a small error against 31P and is tied versus 42P.
11 is fairly easy. Near or 8/7(2), 6/5(2) is usually right unless you leave a direct shot. Otherwise you play e or 24/22, 6/5(2).
31P 11 appears to be the exception. e just so slightly wins the rollout war versus 31P with N being tied. A reverse split makes sense against the best priming roll 31P, plus you leave 7's to get hit, so this is probably the reason. Still, it's probably easier to just remember the rule and be slightly off one time than to try and remember the exception.
22. Go with Near or 13/11(2), 6/4(2) versus 42P and 61P. The reason I believe is that with your joker 22 you have the better priming game. This isn't quite true against 31P so E or 24/22(2), 6/4(2) makes the most sense. Here you advance the anchor and neutralize his prime somewhat.
33 is played the normal way, "up and down" or 24/21(2), 13/10(2). This is impossible against 42P. here your best bet is make the board with A or 8/5(2), 6/3(2).
44, 55, 66, and 65 are all obvious.
*** Blitz Structure ***
53P is a halfway-house, where the opponent could prime if he rolls well but he is more geared to attack.
Slotting with aces is the wrong idea (but note it is not as bad equity wise as you might think).
Splitting wins the rollouts but Two Down is a reasonable alterative (and logical too since he would like to attack you on the 4 or 5 point).
54S is probably right even though you put a juicy target inthe attack zone simply b/c 54D is such a clumsly attacking play. But the plays are tied.
Note reverse splits are good. Hence 43Z is logical (make progress on all quadrants and split to the point he last wnats) and best but 43D is also logical (prime, don't split to the attack zone) and tied.
32S is also best (reverse splits are good again!) though two down is only a small error.
Definitely make a point with 64 - he makes an attacking point, so do you.
52 Split is clear. Reverse Split (yes!) and 52D is too fugly really.
Split with 63 and 62 is clear. Running when behind in the race is wrong concept. Note 62$ or slot is wrong but reasonable. Idea is you keep the anchor so can't get blitzed and you try to prime, which is strategically sound.
64P is definitely an attacking play. Opponent is clearly attacking, not priming. Note the 8-point and 2-point can not be part of the same 6-prime.
Down in the race, priming is clearly the correct strategy.
Therefore, slot with aces.
Two down is clear with the split or slot rolls (54, 52, 43, 32). You especially don't want to split into the attack zone with 3's and 4's as the opponent will happily hit you there. Note 52S is tied with 52D, probably due to the power of the reverse split once again.
64P is the only consideration. Mirror your opponent's play.
63 and 62 suck as rolls but you gotta play them.
63S is really the only play since you are behind in the race.
62S is best on the rollout but 62$ is tied in the rollout. Strategically again this makes sense. You are behind in the race so priming makes sense. Also you are outboarded so giving him a blot as a target (when you split to his bar point) may not make the most sense.
Doubles are all played as normal.
11 and 22 Near. 33 and 44 up and down. 55P and 66B are obvious.
But note 22E and 33A are only small errors. In the case of 22E you advance the anchor and reduce the power of future hits as well as place his checkers on the 2 point out of play (behind you). 33A is a slight error but a reasonable play, probably since you are beating the opponent at his own game. By making a 3-point board you are better prepared to attack than the opponent.