Extend duration of imported PSD "footage" layers
I have imported a layered Photoshop file into After Effects as a layered comp with several .psd "footage" layers:

I've created and edited the comps within the 20s main comp with animations and effects. Now I need to extend the .psd layers(all ~7s) to the length of the main comp(20s).
I've tried dragging to extend their regions and right-clicking > Time > Enable Time Remapping(this allows me to extend the region with keyframes, but the content still ends proportionally short of the containing comp duration).
When I right-click the .psd layer and click "Open Layer Source", the preview shows the layer duration extending to the same time as it shows in the timeline(~7s)...

but the green "render bar" only goes to 5s. And no content is showing while the playhead is at 6s, below...

This is also reflected when I drag the playhead in the main comp timeline—the layers with this problem disappear at 5s even though their regions extend to 7s.
1. I need to get these layer regions to extend the length of my 20s comp.
2. It seems like the layer source only goes to 5s when I "Open Layer Source", so even though the region currently extends to ~7s, the 'content' only goes to 5s.
How do I get extend everything to 20-seconds without doing all of my keyframes/animations/effects over again?
Or is there a way to re-import just those layers at a longer duration, but keep all of my keyframes/animations/effects.
Using the latest Photoshop CC 2015.5 & After Effects CC v2015.3.
Thanks!

