If the holding brake doesn't work, just open it in the editor, open the brake's settings and slide the "position on section" slider SLIGHTLY towards End. It's designed to hold the train in place precisely at the point where it naturally stops moving upward, if the train is going slightly too slow it won't reach the trigger point and the brake won't activate.
This is my first attempt at a shuttle coaster, mainly to figure out how to set everything up properly, and I wanted to make a good coaster out of it that's more than just a clone of existing Inverted Impulse coasters.
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