Situation:

I have built a large number of units made from small props all parented together. It is not feasable to convert them to figures... they work better as props.

I need mirrors of them.

Is there a way to mirror them all in one operation, and preserve the parenting structure?

PhilC has a very good prop mirror built into his Power Tools suite, but it only mirrors the selected prop... not those parented to it.

Any suggestions?

If not, I'm in for a long week. There are 250 of these things!

Actually, that is a simple one.

Export wavefront obj file.
In your export select all of the props. => Poser will save them out as a single obj file.

Goto Blender, mirror, export as obj file.
Open Poser, import mirored obj file.

Sorry... won't work. This destroys the morphs and bends built into them.

Correct, this only works with static props with no morphs or bends.

Depending on the props???
Look at the scene from the other side?
Turn the camera 180°

I dont know if it will work for what you are doing, but I have used 'mirror prop'  script with good success

load your props, create a grouping object, parent the props to the grouping object, and mirror the grouping object

Bill

You might also want to check out Dr. Geep's site, or contact him.  He deals with creating scenes and such with props extensively.