If the sole proprietor's NOW account was to be for business purposes, Reg. DD would not have applied and you could do whatever the bank wanted without a violation of the regulation.
Exceptions to retain business for consumer accounts would not cause a problem, either, as long as you did all the things recommended above, and didn't make it a practice.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8