[McKay (OP)]

Have there been measurements of the Casimir effect at different altitudes on Earth, in orbit, in interplanetary space? Is there even reason to think it might vary from place to place?

What got me thinking of this is "Einstein's Missing Inch" - the fact that massive objects warp space and so the circumference is smaller than pi*2R. That kinda means there is .. umm.. more space density, for a lack of a better term, in certain regions and with that might come different strengths of the Casimir effect.
if not that, maybe something else, just curious.