I actually made two of these, but not because I wanted to.
I bought a heavy white cotton fabric, both times I made it, which worked well> But the second time I bought padding, both for the cummerbund itself and for the pockets, and it's made a world of difference to the way it looks.
I used the pattern available on the Studio Creations how-to site (
http://www.studiocreations.com/howto/bikerscout/index.html) to start with. From there, I measured out how wide it would need to be to look right on me (since the measurements are for men, and were much longer than they needed to be, but maybe not quite as wide, since women - and especially me - have hips). I created a mock up, tried it on, and gave it the seal of approval. I used this method both times, with great success.
The first time, as I mentioned, I didn't use foam, and the foam makes all the difference as far as I'm concerned. Without it, the cummerbund looks flat and lifeless, is droopy and doesn't really look like a part of an 'armored' costume. The foam gives it a more canon look, not to mention giving some life to the damn thing. Bad enough that it already looks like a diaper!
The foam I used was approximately 1/2 inch thick. I could have gone down to 1/4, but I think the 1/2 in actually works out nicely. I made sure that my mock up, and the subsequent fabric cut allowed for enough room (but not too much) to slide the foam in tightly when the seam allowances were sewed up, and then amde the codpiece type deal as well, along with foam and seam allowances.
I sewed the belt part and the codpiece part in two separate pieces, and then attached them after both were done. The resulting piece looks more like the movie shots to me, and just generally looks better the way I see it.
I reused the original black elastic from my first attempted cumberbund (approximately 10 inches, with velcro on the inside of the cumberbund. I also closed up the back using velcro, soft side on the outside part that would be covered, and the hook on the inside part. I did an overlock stitch on the edges so I wouldn't lose any more length, and the resulting look I personally like. It may not be for everyone, even if it isn't very visable.
The back velcro I did vertically, although in hindsight (and I may even change it) I'd do it horizontally - at least as a woman. With hips, the whole cumberbund equation changes!
I need to take pictures of the new one, and then post pictures of both still. I'll do that this week.