Can MailStream Plus assign Retail postage rates for un-qualified non-Commercial First-Class letters

MailStream Plus™, all versions, all platforms
A mailer had 261 pieces of First-Class 1 oz. letter mail, which is below the minimum required 500 pieces to qualify.
MailStream Plus™ (MSP) correctly put the pieces onto the 3600-FCM Postage Statement line B5-"Nonpresorted/Single-Piece*" and gave them the rate of .500 per the USPS Notice 123 Price Chart.

The mailer said that the pieces were not commercial mail, and were going to have stamps put on them.  He wanted the rate to be the Retail letter rate of 0.55

There is no option in MSP to do that, since line B5 is the correct line for the pieces, and .500 the correct rate.
Part of the reason for the results is that MSP is not designed (with some exceptions) for Retail Price mailings.
UPDATED:  February 5, 2019