Lid for Shadows of Brimstone Holder

These lids fit the large and small Shadows of Brimstone token holders as presented by http://www.thingiverse.com/BasHamer/about BasHamer, here:
http://www.thingiverse.com/thing:1949810
and
http://www.thingiverse.com/thing:1936589

These represent my first forays into creating 3D objects, and as such they are by no means perfect.

I would suggest making the flat 'top' an extra 1-2 mm thicker, and editing a channel down the middle to allow for an elastic band to sit flush with the top inst