pog - I can't help feeling this issue is connected with the situation you describe on the other thread....trying to keep your baby feeding at scheduled intervals, and feeding him after he has been crying and rooting for a while.
Crying can be a late sign of hunger in a newborn, and this in itself can cause the baby to take in lots of air.
On the other hand, feeling and hearing wind in a baby's tummy is miselading. If you put your ear to anyone's tummy you will hear all sorts of gurglings and whooshings, and the natural contractions of the internal organs can make tummies feel hard, without it necessarily being a sign of uncomfortable wind.
Lots of skin to skin contact, and practice at feeding when your son is not crying, encourages happy latching and happy feeding.
There is no point in expressing, as far as I can see for this; however, maybe you are showing signs of over supply, which can sometimes mean a baby gets overwhelmed with the let down, and pulls off to try and cope.
Try going with the flow for a few days and seeing if it makes a difference