I started stressing about this last year as well because I only had enough time to write about 2 other texts. I rang up the HSC help line last year about it, and the person I talked to stated that 2 other texts should be enough (this was for English Advanced). I think you are better off doing 3 other texts, to show the knowledge you have for variety of texts that relate to your module (I managed to fit 3 other texts in detail somehow after some practice). You're given an hour to do each question, so their is a higer possibility that they could ask you to do 3 texts (as opposed to 40 minutes in English adv), but it has not been done in the past.