Having recently repainted my Rubies helmet I thought I'd give the inside the 'once over'. I gave it a new visor (the old one was REAL bad) as well.
Here are some pics of what I did ... essentially I followed the layout of the Riddell helmet inside (no sense going with one of those fantastic Marrow Sun kits on a crappy Rubies!!). I started with foam from a local craft shop and cut the foam to the desired shapes (lots of cutting and trimming to get the right size and thicknesses) and spray painted them. Then I glued them into place inside the helmet.
Rather than go with a hardhat liner I added more foam pieces until the helmet/foam fit comfy on my head. In the end it turned out okay !
I had to work around my switches and fan which I had already glued in place, but that didn't end up being too big a problem.