Is it possible to have the thumbnails overlay the main image without using the fixed layout option?
No. Without using a Fixed Layout, you can position the thumbnails only by using the thumbPosition configuration option, the values of which can be TOP, BOTTOM, LEFT, RIGHT and NONE (all of which are relative to the main image).
Also the thumbnails seem to move relative to the image and dont stay in position relative to the stage, so for images of different sizes in the same gallery the thumbnails move around.
Take a look at the lockTopStack and lockBottomStack options (in the General section) in conjunction with the Locking Stacks section of the 'SimpleViewer-Pro Layout Guide'.
For example, if you set thumbPosition="BOTTOM", then setting lockBottomStack="TRUE" should prevent the thumbnails from aligning with the main image when the width of the main image changes.
SimpleViewer Support Team