Do we need one or two DEV transactions?

Line 245:  There should probably be only one transaction.  The ack for the heartbeat would just be to the DEV-53, DEV-54 is not needed for an ack.  DEV-54 could be used for unsolicited messages from the consumer to the reporter, i.e. PCDC communicates its participation in the MC to the PCDR?
In section 14 after line 265 #1,2,3 would be DEV-53 while #4,5 would be DEV-54