I don't mean to piggy-back on to your post, tomfireburns. However, I would like to post a reply to SprinklerGuy. In my area, which is about 40x40, with semi-clay soil, this area is pretty flat with a kidney bean shape island close to the middle, yet ofset a little to the side. The shape as mentioned is square.
The initial estimate I received was with spray heads every 12 feet and three in the middle. Although I can see some benefit from this, I can't see why I can't use rotors for this area. The only obstruction that I can possible see is two boulders about 2 feet high in the middle of the island. Don't rotors typical spray higher that this? Are they trying to sell more parts than needed?
Thank you for letting me add to your thread. I am interested in any comments.