That's good that you think I have the right face for it, it might just work then.
The mark IV suit didn't have as many uncovered areas as the mark V, and the mark V does look like it has lots of kevlar padding on it at the abdomen area, but this is covered by a gun metal grey metal part on the mark IV. The only uncovered areas on the mark IV are the joints. Thanks for the links, some of the helmets look somewhat like the helmet of this costume, so perhaps one can be made from one. Yes, I am going to make the helmet. Most people don't know whether they should make one or not for a costume like this, but I've seen a photo from the first game of him wearing one, so he did have one. Though he possibly didn't wear it on his adventures, all HEV's came originally with a helmet even though you wear it later or not.
The orange parts always seemed like metal to me too, but also looks as if they are painted metallic. Possibly they could have been painted candy orange and looked metallic since the parts are metal, but my parts will mostly be fiberglass and plastic, so metallic paint will be the best then. Well...They didn't really paint it anything since it doesn't really exist...
I yanked this off of my post at the RPF:





Looking at the hand plate, it looks much more like the light is being diffused over a metallic surface rather than plain orange paint.
Metallic:

Plain orange:

It looks as if plain orange doesn't shine back yellow but instead white, and the HEV suit shines back yellow pretty much and looks very much like the metallic car up there.
I also saw a really well made HEV mark V out there that was totally..game accurate?
And it was painted metallic orange. I have never seen the person who wore it before, and my guess is that if he was capable of making such a good costume, then he would probably have had training by building many other things before this, and would most likely be a member of the RPF, but he's not. Therefore I think that suit might be a promotional costume made by someone hired by Valve to draw attention to the games that he is standing next to in the photo, so it they were told by Valve that the suit is metallic orange, then perhaps that's the right paint for this?