Discovered this by chance, and I find it does help me:-)
When watching the Page Turn Tutorial - the part where the front cover is made to turn over to the left - I noticed that it wasn't really easy to keep the cover lined up against the spine. Sure enough, when I tried that part myself, I found it very difficult, and could not find a way to just "nudge" the image a pixel or two (like Ctrl with one of the arrows in PSE).
I am working with 1920 x 1080 images. I started opening a blank, transparent document in PSE, 960 x 1080 pixels. I placed the spine against the right hand edge, then enlarged the document size to 1920 x 1080 pixels.
For the cover, I again made the transparent document 960 x 1080, placed the cover image to fill this document, then enlarged the document to 1920 x 1080.
Closed PSE, opened PrEl, placed the spine on track 1, the front cover on track 2.
I placed keyframes at the 2-second mark with all the settings in the Basic 3D set to 0.0
With the marker on the 5-second mark, I set the Basic 3D to 90 degrees.
The front cover opens beautifully, without having to nudge the image to stay on its "axel"
I'm sure this will work with the pixel dimensions for other formats as well.
My next step is to add the first two pages with images, to both show when the cover is all the way to the left.
Esther