I'd have to say "no." Under the regulation (229.13(g)), if you don't provide a required notice of an exception hold to the depositor when the deposit is made, you generally must mail or deliver the notice to the customer as soon as practicable, but no later than the first business day following the day the facts became known to the depositary bank, or the deposit is made, whichever is later. In your scenario, it appears the decision to place the hold is made later in the day on the date the deposit is made, which would call for mailing the notice on Business Day 2. You're mailing them on Business Day 3.
It would seem that the holds should be placed before the processing of Day 1's deposit so that any notice might be generated during that night's update and available to mail on Day 2.