You can delete the body part. That will leave just the sub-summary parts.
Go to Layout mode, Layout menu. Part setup. Click on the Body Part and delete it.
Like this? Ray Cologon comes up with these kinds of ideas long before the rest of us know we need them! It says FM 9, but works for all versions up through the current one.
Dynamic Layout Technique
This will do what you want. Basically, your "body" fields are in another subsummary, but sorted by the Unique Primary Key of the records. Sort this field and the "part" appears. Remove this from the sort list, and the "part" disappears.
While you are there, take a look at some of the other demos Dr. C has provided.