I remember having a similar question in regards to constraints for rotation. And I just managed to find Mark's answer. (Setting constraints into the needed position can be really tricky otherwise.) The problem is, that when leaving the modeling room, your model will be re-orientated from its initial position in the assembly room. So you'll have to re-tweak things yet again. (Now if you made the model in Carrara, you can probably disregard this since it should be lined up.)

If your origin axes are already lined up, but not quite centered, you might find Sparrowhawke 3D's Transforms Package plugin to be of some use. It's very nice considering the price!

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.