Will the hammock task work for you here? The problem I see is that you cannot in turn make 2nd product the driver for the 3rd product - overwriting the finish date for one task will break the link. Is 2nd Product dependent upon First Product? If so, a F to S link is in order - not a hammock task.

Yeah it's a pretty typical chain of products. Although in many cases there are other products that come in from another area.

1st -> 2nd -> 3rd
/\
¦
4th---->5th----


The connections I'm using are finish to start already. The problem being if I change the end date on 2nd or 5th task in the above example, the task gets pushed forward rather than the duration changing, despite the fact that it did usuall start on the same date.

edit: ASCI fail. The line fromt he 5th task should be leading up into the 3rd task. Can't get it to format correctly.

If the task really started when it was planned, set an actual start date and it will not move. I suggest tracking the project to supply actual data and then re-projecting the finish dates.