Epiphany
Like my header there says - I haz it. Just now.
The cheek details on Sharkhead & Dubean's awesome HD Iron Man helmet were driving me absolutely INSANE. And then, after letting it sit for well over a month and coming back to take another stab at those pieces with reprinted pages, it was like a lightning bolt - TRUST THAT THE FOLD LINES ARE PRINTED CORRECTLY. Yeah, it sounds stupid - hell, it *IS* stupid. At least, it's stupid to think that there's no way the folds can work out properly the way they're printed, because dozens of people have already built the thing, and I haven't seen ANYONE saying, "Well, you need to reverse the folds on these parts for it to come out right." - just trust that the lines are right, and make your cuts and folds PRECISELY. For the cheek details, it actually doesn't hurt to trim the flaps down from the size that they're printed, but make sure that you're trimming the flaps, and not the part. A few hours of off-and-on work on the reprinted pages, and I'm nearly through with one of two beautiful cheek detail parts needed to allow me to start actual assembly of the helmet from the pile of subassemblies I currently have.
Learn from my fail.