Hope you have the lowpoly as body_low_0 as well... Having the _0 on the highpoly is changing its suffix altogether, and won't match the suffix of the lowpoly.
Yes true, it's almost better to look into it and figure out what is causing this. This could be the normals of the Highpoly or the cage. Have you conform the normals ?
That's badass, i agree with the optimisation but you're probably using this as the highpoly mesh? The design reminds me heaps of his baterang which is great.