Dave,
We are currently installing a new 5 Row irrigation system at our club. With the 5 row system you have a little more flexibility and coverage area mainly for the rough areas.
In our design, we'll have a row down the center of the fairways and then 2 parallel heads in the edge of the first cut/rough on both sides, very close to each other. The most outside row will be strictly for the rough, while the head closest to the fairway, will give coverage for the outside 3rd of the fairway and also some rough coverage.
Hope this helps.