I'd be tempted to use one of these APEM MTG72AD2 switches in the end of each extension:
Centre position is off. Move up to change up, move down to change down. They're even IP68 rated. And the OD is just over 22mm, so the perfect size.
@Brommers started
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I'd be tempted to use one of these APEM MTG72AD2 switches in the end of each extension:
Centre position is off. Move up to change up, move down to change down. They're even IP68 rated. And the OD is just over 22mm, so the perfect size.