Hi sneather, also another possibility is using the "Vertex Normal Tool" plugin for Cinema4D from here (scroll down to the second item on the page) :
http://frostsoft.blogspot.com/p/plugins.html

That plugin looks like it has a way to flip vertex normals in it, maybe that could be used to fix the vertex normals after you've used the regular flip command in C4D.

- Michael

Thanks, Michael. Yeah, the model is a little less than perfect. There are, indeed, some naked edges, as whomever was responsible for this product, didn't seem to model as well as they could have. However, not so many that I thought it would be a problem, but clearly, I must have underestimated that impact.

I wish I could just solve the problem in C4D, but the real issue, is that I'm using normal maps in my materials, and that immediately reacts to the opposing normal and vertex maps. And, yes, I've pestered Maxon for years about this flaw, and I've never even received as much as a response. They seem to focus on new features which look good on a sales page, but often neglect core details which make our lives hard.