This capability was not implemented in 5.x, in the port from 4.x. I have added this item to the bug tracker xaware-Bugs-#2039284.

You could try converting your Copybook Bizcomps to use the Multiformat Bizcomp instead, which supports reading from text by setting xa:source_type="message" (and setting xa:record_source to a text value).

How many Copybook Bizcomps like this do you have? Would you be able to accept a Copybook change in a 5.1.1 point release (5.1.0 GA is frozen, and being released tomorrow)? We could probably provide a daily build for your testing, prior to an official point release. By what date would you need the Copybook changed in order to use it instead of the MF Bizcomp?