The problem with that approach is that it's hard to get convincing shadows. Shadows from the layer in front of a flat one will not fall 100% correct. In most cases it doesn't really matter, but the "imported object" doesn't suffer from that. On the other hand it is of course higher in polycount than a flat square :o)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.