See the thread the past couple of days in the Sales board about printing invoices.  The next update (I hope this weekend) will add from/thru Customer Class to SO-B, SO-C and SO-F.  Can you use Customer Class to group the customer types for printing the packing slips?

It may be too much work at this point to convert, but we use the class codes in CM-A to sort customers for marketing purposes. Two huge advantages of the CM-A ones is that you can only enter approved codes, AND you can add descriptors to them so that you don't have to keep a lookup list.
 
And now that CM-A and AR-A are (or can be) synchronized there's no good reason I can think of not to use CM-A.