The original modal here, might, allows for the correct past-tense interpretation, whereas the may introduced in the 1841 British edition forces a present-tense interpretation, an obvious error. The subsequent LDS edition (1849) restored the correct might. For a list of other cases where might and may have been switched in the history of the text, see under Jacob 5:13.
Summary: Maintain in Helaman 3:11 the original might, the appropriate modal for allowing the past-tense interpretation in this passage.