Here's another strategy computed from the paper: cooperate with probabilities (0.9, 0.7, 0.2, 0.1) in the case (CC, CD, DC, DD). Supposedly this strategy is one that sets the opponent's score to an average of 2, regardless of his or her actions. You could come up with a similar strategy to force any outcome in the interval (1,3), excluding the endpoints.

I've yet to check how this works.