If I could stand all night that would be great but I couldn't do that, I'd always end up with a sore back.

To maintain maximum height while sitting I bought a folding barstool at IKEA (seat height is 38" and it's a smart modern design) and, setting my X-stand at maximum height, I find that I'm visible enough to the audience - no one has ever commented that they can't see me.

The only drawback is that having the X-stand at max height obviously makes the keyboard somewhat less stable on its legs, and my EC5 pedal only just about fits between the feet, but I can live with that.