The layout of the subreports depends on your main report structure. If the main report is grouping on some data requirement such as job name. Then you will want to tie the sub report so they will run part of that initial grouping and thereby keeping the right sub report data with the right main report.
A possible layout thought.
GrpHdr1
GrpHdr1b - subrpt 1
GrpHdr1c - subrpt 2
GrpHdr1d - subrpt 3
and so on....
Sometimes because of the calculations you need to perform and the way CR makes its multiple passes in generating the subreports you may find it necessary to use the GroupFooter sections or add additional Detail sections to the report, then place the subreports into them.
There are probably other ways that are better, perhaps Hilfy or Brian will improve or correct my suggestion.
Regards,
John W.