How should White play 66 here?
As always when you roll doubles you will have many choices.
When you consider any roll that hits loose on your 1 point, it must be better to simply make your 1 point with 13/1*(2):
This gives you a 4 point board with one of your opponent’s checkers on the bar.
If they do not enter, or enter but fail to anchor you should be able to continue attacking. The problem with this move is that if your opponent does roll a 4, then they will be in good shape and you will have lost control of the outfield and will be scrambling to put your game back together.
The net result is that although it is great when your opponent doesn’t anchor, when they do you are in such a bad way that you have to discard this play.
You would like to get the checker on your 22 point moving, so you consider 22/10 13/7(2):
This aims a lot of firepower at your 4 point. This will be really good if your opponent does not roll a 6 or 51 and hit your checker on the 10 point. Your position is far from ideal if your opponent simply makes their 21 point anchor. Again, the issue is that you have given up your midpoint and therefore lost control of your outfield. You need to keep your midpoint here.
So, you want to get your 22 point moving, you want to keep your midpoint and you would like to hit to win Gammons. You would also like your opponent not to anchor on your 21 point.
Consider 22/4 11/5:
You will not like being hit, but if you are, then you will still have your 20 point anchor and your midpoint.
If you are not hit here and your opponent stays on the bar, then you will be too good to double because you will win about 45% Gammons.
This is the move that puts your opponent under the most pressure, while retaining your structure as insurance against being hit from the bar or future bad luck.