Very good post.
There are some things that you will be interested in....mostly by Morten Rand-Hendriksen; check him out on codepen. He also has a very good presentation on Grid on Youtube at youtube.com/watch?v=txZq7Laz7_4
In relation to @supports for Grid he makes a good point and suggests using @supports (grid-area: auto) rather than simply @supports (display: grid) because some older browsers support an early version of grid which will be triggered by the simpler version.
You will also notice in his pens that he illustrates a working solution to stacking grid items for which you state in your post...
Notice how we did not use grid-area for .meta element. That's because, for now, there isn't a way to superpose elements using this method. At least not that I'm aware of.
Flexbox and Grid provide a lot of the features that have been on my wishlist for a long time.
It seems to me that the more these languages develop, the more they seem to be getting back to way programming once was. Pretty soon, I might be current again.
I look forward to more posts
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