If you project the image onto your model from the Photomatch tab, and they are not rendering as expected, try selecting "Texture>Make Unique" from the context menu for each face containing a projected photomatch image. This should not be necessary in most cases.
- open the original image used for the photomatch in SU "original" inside your photo editor of choice
- figure out exact Height in pixels of orig. image
- render your model with exact same resolution or greater by choosing the same height as original
- save the image "PMatchRender"
- select your entire model
- render alpha mask "PMatchMask" at TWICE the resolution of the PMatchRender image.
- in your photo editor resize the the PMatchRender image AND the PMatchMask if necessary to be exact same height resolution of "original"
- add an "alpha mask" channel to the "PMatchRender" layer
- now add the "PMatchRender" in a layer on top of the "original", now you should see them aligned perfectly