Hi jon
This thread has been up for a while so I figured I would take a shot at it. I am just getting into this sport myself so take this with a grain of salt...
When I pack it also feels unconfortable (I think this is normal) so I only pack a little (1 or 2) when just swimming in the pool. However, it feels MUCH better when I dive down even in a small 17ft deep diving well. I suppose the volume reduction in your lungs contributes to that when you go even a little deeper.
As far as contractions, I cannot help you there since I am trying to figure them out myself at the moment
