Despite this being my first post, this is actually the second (maybe third, depending on how you count it) piece I'm working on. The forearm pieces are assembled and sitting in the shop awaiting paint; I'll post some pics when I manage to get down there and snap them.
In the meantime I'm working on the lower leg (technically the right lower leg, but the two sides are symmetrical -- at worst, I just flip the pattern over). I want to continue the approach I used with the forearms: construct an inner "fit piece" and layer the details over it. Unlike the forearms, some of the fit piece might be visible this time -- I'm using this image from the Gaming Heads' Gordon Freeman statue as inspiration and the fit piece will approximate the gray curvy bits on the back of his calves.
With the forearms, the fit piece was just a cylinder, which I was able to eyeball and test-fit without much fuss. The calves are more complex, enough so I can't eyeball it; my brain just can't visualize the curves required. I have a Pepakura file supposedly ripped straight from the game, but I don't like the shins in it, so I'm trying to roll my own.
So I took my leg measurements (length from knee to ankle, plus circumference at the knee, calf, and ankle) and put together a rough Sketchup model which I then transferred to Pepakura Designer. Here's what it looks like:
Not too fancy, but it's a close enough approximation to the statue's calves for my needs. I should be able to construct it in just two pieces of foam, which will help keep things simple.
I tried to keep it with a reasonably low polygon count so the Pepakura wouldn't be too complicated. Hint: use closed polygons instead of circles in Sketchup to keep the poly count low.
I played around with the scaling until I got something I thought would work, then printed it and transferred the pattern to 5mm foam. It was way too "fat", but the height and calf-bump-out proportions were about right. So I trimmed material from the front until the diameters looked right on my leg. I trimmed from the front because I intend it to be open anyway; this is how I'll get my leg in and out and I'll hide the opening by velcro-ing on the orange shin-guards you see in the statue picture.
Here's the prototype fit piece as-constructed: