Did a bit of testing on MacPro 8xCore 3G with internal striped Raid.

I get two 1920x1080 movies running at constant 25 fps with Photo-JPEG 50% and still one 1920x1080 movies with Photo-JPEG 75%... not too bad.

I also tried the "Run test" option but there I saw some drops to 24 fps (1 Layer) something like every 10 seconds.

For the "preview layer" to sub-mix routing it would be a nice to have if the Layer selection from the "Mix options" would activate / deactivate that layer in the preview...

Some really nice add-ons - nice works Richard.