I would argue that no cast should ever touch any part of the body, or clothing. It's as simple as keeping the line moving only on the downwind side, hence the need for offhand casting per this discussion.
Not meaning to split hairs on the topic as that is a fine piece of headgear, but on the topic of casting I would stand firm to that, particularly as an instructional note to a new caster to instill the thinking early, etc.
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