its actually alot of fun. not quite the real thing, but very addictive if you enjoy flying your body and want to get good at it. but the most return participants are probably experienced skydivers who after spending a few thousand dollars on some bulk hours would reach a point where they want to take their newly honed skills back out into the more expansive real sky.
having said that, there is a small niche emerging of competitive tunnel-flying, mostly for people who prefer the indoor experience for whatever reasons, which may eventually grow into a bigger sport.
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