VrayEdges Tex behave differntly when used in a composite map?

[simmsimaging]

Trying to use the VrayEdges texture to round some corners on a box, but I have to blend it with a couple of other bitmaps for the full bump effect I need. It doesn't seem to work well when used in a Composite map though - does it behave differently when it's not used in isolation, or is it just me?

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