This article basically argues the theory that nothing can be done to help catnapping. I wish I had read this article with my first baby. Looking back I can see that the amount of time and energy I spent stressing over trying to get my DS1 to nap longer than 20-40 minutes was such a waste. He started napping longer when he was ready. I totally suscribe to this theory now that I have a second baby whose sleeping pattern is entirely different despite ME doing nothing differently. (DS1 didn't sleep through the night until he was 11 months old, and DS2 slept 9pm-6am from 6 weeks old!!). I think those books that suggest something can be done to improve catnapping are very harmful.
I just wanted to share this with anyone stressing about what they can do to help their catnapping baby. I don't know if it helps much to say you just have to wait it out, but I think it would have helped me to know it wasn't anything I was doing wrong.