Money Play. How should Red play 31?
23/20, 21/20 is too passive. It allows White to make Red’s bar-point most of the time, from which he could go forward or backward.
Red needs White to commit to a back game and therefore 8/7* will be part of the answer. After that there is very little difference between 23/20 and 12/9 for the 3. The key is to hit with 8/7* to attempt to force White into a back game. If things go well Red can build a prime and force White to crunch his home board but that is only one of very many possible outcomes from the starting position!
Not an easy problem by any means.