This is a good example of the differences between making a 3D model for a game, and making one for papercraft I think.
The rim of the cap is a little bit wider than the cap itself, which creates a nice effect that I'd like to keep.
In a game, you can just suffice with a hollow shell, but if you would try to make it into a papercraft model like that, you would have to make a very thin strip of paper with a lot of awkward valley folds...
In this case, I think it would be better to close the "rim part" of the cap and make it into a flat, closed disc, so that you can simply glue the cap itself on top of the flat surface.
I often use this method and although it works pretty good in many situations, when making a papercraft model it's up to you to figure out what those situations are. ;o)