SQL question on chunking aggregates

Hi all:

I have a table that has multiple records for a single owner_id. I'm able to use array_arg to combine the records into a single row, which works fine. I'm using this sql:

select owner_id, array_agg(trim(maplot)), array_agg(revallandvalue + revalbuildingvalues) from parcel group by owner_id;

Which results in the following (sometimes there's only one record per aggregate, sometimes multiple):

1030600;"{"154 191"}";"{244690}"
1030900;"{"22 202"}";"{217210}"
1031130;"{"113 135","113 138","113 132","113 130","113 133","113 127","113 126","113 131","113 129","113 136","113 125","113 137","113 134","113 128"}";"{7700,7700,7700,7700,7700,7700,7700,7700,7700,191770,7700,7700,7700,7700}"

What I want to do, is where there are more than 5 rows involved in the aggregate, as in the last example, to split it into multiple rows of 5 aggregated rows. It's for a mailing list and I want to combine like addresses into one record, but if I'm over 5, I have to print the rest on a separate letter.

1031130;"{"113 135","113 138","113 132","113 130","113 133"}";"{7700,7700,7700,7700,7700}"
1031130;"{"113 127","113 126","113 131","113 129","113 136"}";"{7700, 7700,7700,7700,191770}"
1031130;"{"113 125","113 137","113 134","113 128"}";"{7700,7700,7700,7700}"

It looks like I should be able to use the window function to do this, but I've been unsuccessful. The following runs, but doesn't seem to have any effect:

select owner_id, array_agg(trim(maplot)), array_agg(revallandvalue + revalbuildingvalues) from parcel group by owner_id
window mywindow as (rows between current row and 5 following);

Does anyone have any suggestions on what I should try?

-Owen