I have a summary field that does a Total on a related table and beautifully prints the correct value for wherever I put it on a sub-summary report. Very nice!
The only issue is when there is no related record in the many table. In this case the summary field is just blank. The "hide when" didn't hide the summary field in the one part of the report where it was blank (no Total in the many table).
I don't see a way to set the "show zero" for this type of field so there must be some other trick. Likewise, for a summary field, I didn't see anything useful in "options".
Look forward to hearing back.