You know it is curious that you mention it because I was going to ask you if you can give me a suggestion of how to do it and if maybe you can give me a small help with the rest of the armor.XD.....
I know that it is possible to use craft foam for the inside of the thigh pieces. At one point I was thinking about that, but then never bothered. Then someone on this site sent me some laytex pieces to use so I will now be using those.
Also in my opinion, the HD version of the thigh pieces look much nicer since they have a lot more detail.