Hi
I dont think the way you are trying to work out this problem will take you through. BizTalk would not be able to understand what kind of a record it is as the records 2,3 ,4 are unbounded. You need to have a tag identifier with each of the record in order to let BizTalk know what kind of record it is.
So if your record begins with 002, 003 and subsequently you have to go on the record node and specify the tag identifier. This will help BizTalk identify the record correctly. When you do this remember to reoder your records correctly as tag identifier will not be in the output xml for the flat file.
Puneet