I remember seeing the "mirror" (or mylar sheet?) behind many of the Wersi artists when I used to attend the Dutchland (Pennsylvania, US) Keyboard Shows. I did like seeing the hands and keys - but with the mirror above, you see everything "backwards" ... when he played high notes, you saw his hands seemingly go low (to the left) - easy to get used to though.
I did like the idea - but you need quite a good-sized mylar-sheet "mirror" if you want a wide audience to all see what you're doing.
I do find that audiences seem interesting in "what I'm doing", perhaps more than what facial expressions I have :-) as they often come up after gigs and ask about the keyboards, ask about how it works or how I get so many sounds at the same time (i.e. splits etc.) - people do seem genuinely curious to see "what i'm doing" with my hands and feet . . . (at least some seem to) . . .
But I'm with the others here who said, "No, not another thing to carry and set up!" :-)
Jim
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Genos / Tyros5 / HK Lucas Nano 600 / FTB Maxx 40a / EV ZX1A / Rock'n'Roller cart / Hauptwerk virtual pipe organ / misc other audio & music toys