SCA rules talk about Padding equivalent to close cell foams. I know people are starting to use cotton in various forms and wool felt. I did a helmet liner in cotton batting and after quilting it is probably a little thicker then a 1/2" maybe 3/4" in some places but seems to be more or less equivalent to atleast the cheaper 1/2" close foams.
What have other people come to the conclusion of for cottons and it seems people tend to use about the same thickness in wool felt as it would be in foam itself does this appear accurate to people who've tried it?
Padding equivilent
It seems to me that less cotton/wool padding is equivalent to a layer of blue camping pad foam. That stuff just has almost no give to it unless you stack a couple of layers together. However I've found marshals don't seem to want to pass less than a good thick layer of cotton padding, and at least locally, still question the legality of non-foam helm padding. At least until they try the helmet on...