Dave, I have the trial version. I'm not sure how, but something I did brought up a panel where I could select many export formats, about 1/3 of them had the "Save as 50%" option. I haven't been able to reproduce it since.
My big problems with this product
- Doesn't work with iPhoto or Aperture libraries
- Doesn't work with RAW images
- Doesn't retain EXIF information
The other version on the AppStore (PMK 5) fixed the RAW and Aperture issues, but it's stitching is far worse. The photos I merged didn't line up perfectly, and the merge point looks like the photo was bent.