How do I prevent VSE strips using Image Offset from being cropped before the transform effect can shrink them onto the screen? I am creating a video using the VSE where I show a sequence of screenshots of two devices side-by-side.

Unfortunately, one sequence of screenshots is from a Nexus 7 in portrait mode (resolution 800x1280) and the video I am making is 1920x1080.  This means that the screenshot must be scaled down to fit on screen.

I have a sequence of the screenshots and some overlay elements grouped into a meta strip.  Each screenshot has the Image Offset box checked so it is pixel-for-pixel to start with.

The meta strip has a transform effect strip applied to it and I apply a uniform scale of 1080x1280 to fit the meta strip on-screen.  I do this so that all the screenshots in the meta strip benefit from the same scale and transform, and I can adjust the position of this screenshot sequence in the canvas without having to edit 10 different transform strips (and a growing number of overlays).  Unfortunately, the top of the screenshot gets chopped off.

How do I prevent the large images in the meta strip from being cropped before the transform effect can shrink them onto the canvas?



 (now has copies of the images packed into the .blend, but you'll still need to save them and point the image strips at them)
Consider a preprocessing pass where you just create new Scaled images at the intended final size with a possible transparent border.
Suppose the Blend User had 100 images at dimension (X,Y) where for example (X = 1280, Y=800) and their final render size was .5 times (X,Y). The User might just create a [2nd new] VSE scene to quickly create a new sequence of images at the new size for final use. VSE is used to batch scale images into a new file. GIMP might do the same.  
I might even place the images in the upper right hand corner and leave a transparent border in PNG format. Suit borders to your needs.  Your already use overlays. Thus no further scaling need take place because of a transparent border.  Then many or all of the files would have the same size ... the offset would be different.
Since I cannot see your VSE strips I am not addressing them directly.  So we cant see limitations, if any, of the strip manipulations. They may be some more space efficencies possible if all that were known, yet its not a requirement.
I have not considered file names.
One could claim their is some waste of hard disk space or RAM.  Space may be cheaper than time.