This is a fascinating discussion for me. Whilst I have no smells on in the heads, I do have a sizable quantity of water in this void and have not been able to remove it. I have tried sucking it out with a pump, but to no avail.
I think this void is quite sizable. I have no idea why, and I would like to know why it exists at all.
If you want to see how much water is in it, go close hauled in a reasonable wind and open the locker under the sink. It's tricky to remove the water with a pump as I am always a bit short handed. But I like the idea of the moisture absorbing bags, and maybe I will try doing this when close hauled.
Mike