Do I have to use Dual Beams?

Not at all.
In the test designer, just tap on a gate and you will see you can use top, bottom or both beams.
Having said this, the only reason you might want to do this would be if you were getting split times off a dvice like a bob sled  or similar.
Or perhaps you are trying to run a  Margaria Kalamen Power test, and want to measure when a foot strikes a stair.
In this test, don't use any tripods.

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