David:
I don't think using a second DeliveryChannel will work. The following is an
excerpt from the CPP/A spec:
The ebXML Message Service's syncReply attribute is set to a value of "true"
whenever the 1190
syncReplyMode attribute has a value other than "none". 1191
Even if you have a channel that calls for the use of synchronous reply mode,
the syncReply attribute still has to be set. In other words, it is still
necessary to use the Via element if the syncReply attribute is present only
there, but this constradicts the assumption that the Via element is only
used when intermediaries are involved.
-Arvola