Now that I have the actual 2008 code book and can read the full text of article, it’s clear that 334.80 refers directly to Table 310.15[B][2][a] and not to article 310.15 itself, so the 24-inch rule doesn’t apply to in the case of running multiple cables through the same hole.
I guess we will need to drill more holes to keep the number of current carrying conductors in each hole to 9 or less, for the 70% ampacity adjustment, to avoid having to upsize the conductors. Seems like it shouldn’t be too difficult to comply with this.
