Making knee inserts - Neoprene? EVA? Polymers?

I'm going to be making some of my own knee inserts for my paintball
pants, along with some openable pockets out of canvas or heavy gauge
cotton.  The main reason I'm opting to make my own knee inserts
instead of buying commercially available knee guards or inserts is
simply because of area coverage; while the ready made pads/inserts
look good, I want something that covers a much bigger area on/around
my knee/upper shin (about 15-20cm wide x 20cm high....thereabouts).
Ideally, I would like to be using either http://www.d3o.com/ or
http://www.sorbothane.com/ sheets, but I can't find where to buy d3o
in sheets, and sorbothane sheets are ridiculously expensive.  From
doing a fair bit of research and legwork, what I'm probably going to
use is some EVA closed cell foam (perhaps 20mm thick), and perhaps
some really tough and flexible neoprene (perhaps 2-5mm thick), then
glue these two sheets together.  I'd have the tough neoprene on the
outside to protect against rocks and boulders, and the soft(er) EVA
foam closest to my knee for cushioning.
I've got a reasonable idea about the various materials, but I was
hoping to get some advice from someone that may have tried this
already.  In particular, specific advice regarding materials and
(metric, not imperial) densities (e.g. EVA of density x, and/or
neoprene of density y, or perhaps different materials).  Just saying
"go use some dense foam" isn't going to help me at all.  Obviously the
thinner the inserts are, the better....but I want to adequately
cushion and protect my knees/upper shins.  I was also thinking that if
I was to make these pockets on the outside of my pants, I could
possibly get away with making the inserts a bit thicker?
Any specific advice at all?