The fact that the check is split between multiple accounts has no effect on the legal amount or duration of the hold, but the regulation does not offer you any direction as to how you "spread" the hold among the accounts. Do it any way you wish, but keep your copies of the notices together so they will make sense to a third party reviewer.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.