Is it flat or sloped? You are right on the edge of MP rotator strips being a perfect solution. They should over lap head to head. Use the right and left strips on the ends, side strip in the middle. You should have a head every 15 feet. Best layout would be triangular spacing (google: MP rotator strip layout). That would put you at 3 total heads. Ideally you would provide them with 45 or more psi, if you cant, I would just shift them a couple inches further from the edge of the land.