If you look up WHEN=GROUP you'll find PUSH. PUSH is like OVERLAY, except you can only PUSH data from the first record of the group, or the special ID and SEQ, which represent a sequence-number for groups, and a sequence-number within groups respectively.
It's still using the reporting functions of OUTFIL (so you need the REMOVECC, as you don't want a "report"), but uses the TRAILER2, which appears "at the bottom of each page". So you set the page-length (LINES=) to four (including the total) and format your trailer.
If you don't have regular data, you'll get a mess, but it's the best way for regular data.