500/550 rods are not considered a weak link. Definitely replace the rod bolts with CB750F2 bolts (bolts 13213-KVO-000, nuts 13214-410-003) Rods could be peened. Mine was low 60's on stock rods, however I did buy Carrillo's later as the power ramped up. (not against the rules
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EDIT: Martin, I have experienced "rod stretch" at high rpm. With stock rods build in some extra clearances.