I wanted to dampen the inside a little with something more sophisticated that a pillow. I have seen foam mats which do the same thing, so I thought I would have a go at my own.
I found some of this in the garage, pipe insulation:
so I cut some to length:
a little bit of gaffer tape:
inside the drum:
and I placed the insulation
they needed a bit of a trim to be the correct length, but I put the skin back on
The end result is that it never moves, it dampens both the skins, it doesn't interfere with the kick mic, you can put in as little or as much as you need, it's dead cheap and not a permanent change.
The sound is great and I couldn't be happier.