With March 15 being a Saturday, it appears that the refunds need to be done by the 14th. There does not appear to be any regulatory justification for using March 17, the next business day. Sal Tripodi's book also says as much. Agree or disagree?

First, I do not see it as impossible for any applicable refunds to be returned on 3/15, even though it happens to be a Saturday. Of course, the reality in most circumstances, is that such refunds would not be made on a Saturday. In that case, I agree it should be done by Friday.