The recommendation of the veterans of this forum is that although newer versions can open erlier versions it is always better to complte a project using the version tht originally created it.
This applies not just to PhotoImpact but to all other Ulead software.
I agree with Steve's recommendations but have had no problems opening ufos created in XL with PI 10. haven't tried it with PI 11 because there was no need yet. Generally don't work that way either.