Final Cut Pro: Modifications to Photoshop layers may cause unexpected scaling

If a layered Photoshop image (.PSD) is imported into a Final Cut Pro project, and then later modified in Photoshop (via Final Cut Pro's Open In Editor command), changes made to a layer's content may appear to be the wrong size or aspect ratio when viewed in Final Cut Pro. This can happen with Photoshop layers that are partially, or mostly empty.
When Final Cut Pro first imports a layered .PSD file, it evaluates each layer in the file to determine how it should be handled. One part of this evaluation process sets the boundary size for the layer. Although the .PSD file might have an image size of 1280 X 720, a layer in that file might have visible content which covers only a portion of that area. Final Cut Pro sets the boundary size for each layer based on the extent of visible image content in that layer.
If the Open In Editor command is used to make changes to the .PSD file, Final Cut Pro can update the project to reflect those changes, but the boundary size for a layer remains fixed. Changes made to the layer in Photoshop will be scaled in Final Cut Pro to the same dimensions that described the visible extent of that layer when it was originally imported.
The following images illustrate how layer content might be unexpectedly scaled after modification.

This image shows an imported two-layer Photoshop file in Final Cut Pro's Canvas, displayed in Image+Wireframe mode. The wireframes show that the white background on track 1 takes up the full area of the Canvas. The green circle is a layer in the .PSD file, and its wireframe shows that its boundary describes a square which encompasses just the circle.

This image shows the same .PSD file after being sent from Final Cut Pro to Photoshop via the Open in Editor command. The red circle has been added to the same layer which contains the green circle.

This image shows what happens after the file is saved in Photoshop. Upon return to Final Cut Pro, the layer is updated to reflect changes, but the layer's boundary size and shape are not updated. The boundary which described the extent of the layer's visible content at the time of its import now contains the modified visible extent of the layer.
To compensate for the scaling behavior in this scenario, you can use Final Cut Pro's wireframe handles in the Canvas, or Motion parameters in the Viewer to adjust size, aspect ratio and position. If that's not sufficiently precise, you can prevent the scaling by predefining the extent of the layer's visible content in Photoshop before you import the .PSD file into Final Cut Pro. Since you probably don't want to compromise the look of your project, consider a method such as the one outlined below to unobtrusively predefine the boundary of the layer's content.

Example
1. In Photoshop, select the layer and select a single pixel in a corner of the image. (i.e, the absolute, upper left-hand corner of the image).
2. Fill the pixel with a color that will match as closely as possible the background color in your project.
3. Set the pixel to have 1% opacity.
4. In the diagonally opposite corner, set another pixel the same way.
5. Create the rest of the layer as you normally would, or use this as a template.
These steps will define the boundary of the layer's visible area to be the the entire area - the same as the image's dimensions. If content is added to the layer after being imported into Final Cut Pro, the scaling described above will not occur. And because the pixels are in the far corners of the image, and are 99% transparent, they should be hard to detect by viewers (and will also be in the overscan area, and thus unseen on standard televisions).
Note: Avoid creating additional layers in a .PSD file that has already been imported into a Final Cut Pro Project.
For more information about using .PSD files in Final Cut Pro, please refer to Final Cut Pro Help.
This document will be updated as more information becomes available.