Raptor0137, I forget what post it was in, but we discussed why they say this before. It is mostly for insurance reasons, as one person stated, one of the ride ops said simply, "You don't have to do it, you just have to hear it". So just in case someone happens to have an injury from banging into a support on a banked turn or something, CP can say, we told you to keep your arms inside.
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Times I have "Gone Full Force" on MF: 2
Next CP trip/MF thrill 6/30