Thanks Hans, that's great, and studying what you did gave me a little better understanding of how to approach the settings for flexible layouts. Those changes you made to the grid of action areas or rectangles worked perfectly.
Now, I'm trying to figure out some other aspects of the flexible layout first. Then after that, I'm trying to figure out the best technique for creating the parallax effect, which is going to probably take some form of On Mouseover Continue Timeline actions. I increased the number of action areas from 9 to 45 because I was thinking that would possibly better help with recreating the movement of the page contents in response to movement of the cursor. But I haven't fully thought through the best technique yet. I think it could be 3 relative timelines with 15 pause timeline keyframes each.
Ultimately, I'd like to figure out as much as possible how to recreate various effects in this web app on the different "slides," with minimal to no JS, in this website I discovered from someone else's previous posting in the forum: http://kennedyandoswald.com/#!/premiere-screen
If you can please help me with the next step, which is to set the contents of the page to scale without changing the aspect ratio, as in the Kennedy movie page. I've attached the file, using your updated action area group (with my increase in number of rectangles). This will really help in understanding the differences between filling an entire page with a group without concern for aspect ratio, and putting flexible content on a page that needs to maintain aspect ratio.
Kennedy Recreation.hype.zip (954.1 KB)
I will try and use some variation of the techniques in this page in order to create the parallax and other animations on the page: http://tumult.com/support/examples/Scroll-Animation-Control_by-Survey-Legend/Scroll-Transition-Tutorial_by_Survey_Legend.html
I was going to try and figure out more before reposting, but if you have time, perhaps you can help me.