The Fourth Trimester theory

I wholeheartedly agree with the idea that newborns really need a "fourth trimester" of pregnancy, hence their first three months of life they are essentially not ready for life on the outside. Pregnancy.org has an article written by Dr. Karp explaining his theory about the "fourth trimester" and its relationship to colic. ParentMap has a shorter explanation of this fourth trimester phenomenon.

For a while we tried to follow the advice from the book Happiest Baby on the Block, by Dr. Karp. While his theory of the "fourth trimester" makes perfect sense, his advice on getting babies to calm down only helped us sporadically and it was a lot more work than simply putting baby in a baby carrier and walking around - which had a 99% success rate. I am sure if we were more studious and serious about his methods we would have had better luck. Basically his advice calls for using five techniques to calm your newborn - the 5 S's:

1. swaddling
2. side/stomach position
3. shushing
4. swinging
5. sucking

The thing that seemed to help my son most was being held stomach down, we got the most bang for our buck out of that technique. Other things, like sucking, were pretty unhelpful. He did sometimes suck on a finger but he never was interested in pacifiers.

Any feedback from readers on this theory and whether using the 5 S's made a big difference to them?