[maples37]

Okay, though, for very small hobbyist payloads, though, wouldn't hydrogen balloons be feasible?

Some quick math tells me that you can lift approximately a kilogram of mass per cubic meter (at sea level, anyway). If your balloon's full weight is a half of a kilogram, you'd only need about a large beach ball filled with hydrogen to lift it. That seems like something that would be attainable for an outdoor DIY electrolysis setup.

[daemonologist]

Oh for sure - in fact I believe weather balloons usually use hydrogen (not for demos, but for large scale/daily actual weather purposes). It's just amusing that the regulations effectively encourage use of the more... energetic lifting gas.