BarCode Carrara's UVMapping is more primative than UVMapper so it's not capable of unwrapping any thing beyond say Cylindrical or 4 sided maps. Hexagon has a much more advanced system of unwrapping UVMaps, but does have a few quirks if you own it (I hope this is one of the improvements we'll see included in the next Carrara version).

As an alternative here is UVLayout, still in BEta so it's free with registaration until the final version comes out. It does a decent job, a little better than Hex in some areas, not as good in a couple. watch the videos as it have a hard interface (well no real interface just hot keys really) so it can be a bit difficult to learn. I'm still trying to figure out some of it.

mike