You're right H-Man. The compendium shows her chest plate actually curves around her body, so it does look odd here. I'm just not so good with angular stuff like that, especially from an angle.
The heads, well while I'm quite pleased with Nei, Rika's head does look a bit odd and it bugs me that I couldn't get it right no matter how many times I redrew it. >:( As I've said, my problem is drawing smaller scale stuff. The details are harder for me to do and my movements often feel cramped and the results are pretty rough looking, yet if you look at my last Rika piece, done on a larger scale, you'll see the difference. I always feel the pencil strokes flow more smoothly too.
Anyway, tomorrow I'm going to set aside some time and draw something a bit larger and maybe more compendium-ish. I have a rather weird idea for some Rika art I plan to do later that needs some practice anyway so all the more reasons to go back to basics. Plus it'll help me get over the niggles I had while doing this one.
One thing I will say is that I'm pleased with Nei's hair. Although it's practically impossible to see in the scan here, the colouring is pretty faithful to some of her compendium images.