Re. rubber feet:
I've had some luck with these
Tiny Self-adhesive Rubber Feet Bumpers from Amazon US. (They're not available from Amazon UK, but they took only 8 days to arrive from the USA.)
That's a rubber mat with an 8x8 grid of rubber nodules. (They're smaller than that picture makes them appear. It's not obvious that they're separated; I carefully cut round a couple before discovering that they'd pop out individually!)
They sit rather nicely on the underside, near the corners. (I fitted four, about 5mm in, where they look like they belong.) When the unit is closed, they dissuade the metal/plastic sliding along the desk. (Not completely rigid, but far better.) Of course, when the unit is open, the expanding hinge lifts it off the two rear feet, but the two front ones still keep it fairly steady.
I don't know whether the Gemini's case wears easily (especially the grey coating/anodisation on the metal, which might be very obvious if it wears off to reveal the bright metal underneath) — can anyone with a first-batch Gemini confirm? In any case, feet such as these may help to avoid that.
I don't know how strong the adhesive is, but I've had the feet attached for a couple of days now, in and out of my pocket &c, and they've shown no signs of coming detached. (And if they do, that sheet provides 15 spare sets!)
(It's possible that something even thinner would do. If I get the chance, I might try cutting out short strips of rubber from the remainder of the mat, and seeing if they work as well.)
So that seems to address one of the concerns I raised in this topic!
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The other — the hinge — still worries me; even more so after seeing 1668880's [a href=\'index.php?act=findpost&pid=286245\']experience[/a]… I suggest we all try to take good care of our hinges and not open them too far!