Nothing wrong with using 3D software as a guide Thor.
Have you tried Googlesketchup? The free version is easy to use and outputs line-drawings, though not as vector (I think, maybe others know different) and at quite a low res, but for working out tricky perspective, it's great.
Though the idea of 3D layers is not daft (other programs have them), I think it is unlikely in Xtreme, at least in the near future LOL!
This is interesting, but perhaps of limited use; http://blip.tv/file/358735
Don't be downhearted anyway, this is still a very good illustration and the reflection is only the 'icing', so to speak.
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