IMO leaving the pivot bolt loose will be ok, but it is your call. If you leave it that way, check it periodically.

Belts used to be sold as matched sets but not anymore from what I can tell. Belts in '05 probably were sold in matched (identical length) sets. Were they a matched set? The shorter tighter belt will probably stretch to match the longer one.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer