Double sided or capped clothing will not work as Poser 5 dynamic props because some of the mesh will be in contact with the figure when at the zero pose. Try this, it may not work with every item of clothing because there may still be some intersecting polygons, but it will give you a start.
Load the clothing figure into the scene.
Turn IK chains off, zero pose and zero body and hip translations.
Select a body part. Use the grouping tool to assign all the unwanted faces to a new group.
Invert your selection, and spawn a prop.
Repeat for all other body parts
Delete the original figure
Export the spawned props as a single OBJ. If you are going to use this as dynamic clothing then your grouping is not important. I exported with "Include existing groups in polygon groups" and "weld" selected.
You may have to weld the groups together if exporting does not catch them all. To do this use the weld tool in UVMapper. You could also assign it all to a single group. Save and import it back into Poser and use the Weld Group button in the grouping tool pallet.
Import the OBJ into Poser 5, parent to the figure's hip and save to the Dynamic Clothing section of the Props library.