typically, they are run tighter for mod than stock. the common method of finding your setting is to go loose until it just skips, and then go tighter one click/notch.
you're gonna get mixed opinions, as there is a point of diminishing returns when going excessively loose. too tight obviously robs power, but too loose allows play or resonance on the loose leg, and you can risk rolling the belt over in an impact as well.
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