I fiddled around more after posting and came to a solution that seemed to work. Adding the canvas offset to the scroll to
Updated example file
[url=https://drive.google.com/open?id=0B0Ci6qxowiQWUUU1SVdPMFZqVU0]https://drive.google.com/open?id=0B0Ci6 ... VdPMFZqVU0[/url]
You're example works really well also. I can't tell but I think yours maybe smoother and I don't know why. I played with adding a lerp to the scroll to, and that smoothed it out some.
Now I'm trying to figure out the offset if I throw layerscale into the mix, no luck so far.
As to why I'm figuring it out. No reason really I was playing with Parallax and layer scale and wanted to better understand them.