I've not encountered one of those before, but I'm still using a one of these, which seems like it might be broadly analogous:
https://yacf.co.uk/forum/index.php?topic=85374.0I'm not slim, and also a side sleeper, and the 9cm woks for me and my hips. It's a bit of a balance between leaving enough squish in it and not bottoming out a hip and getting cold. For colder camping I have started putting a space blanket under the mat for a bit of extra insulation. Reflection. Whatever.
The Klymit mat cites a much lower R number. I don't know to what extent these things really translate between manufacturers, but with that big of a difference I'd be having a think about what sort of temperatures I'd be camping in and whether I feel the cold. You might be going for lightweight of course, so whatever your priority is etc etc
Does it come with an inflaty bag thing? Are you fine with huffing moisture into it?
I'm curious about its failure mode too - do they get a comedy massive bulge if a baffle goes?
The side rails on my Big Agnes are enough to cue me it to if I'm near an edge. If I want to find a comfy knee position, they're also small enough that I can put a dry bag or a jacket or something next to the mat and spread out onto that.