One way you could do this, but it won't keep your sidewalk dry, is to install a Rainbird 3500 or the Hunter PGM. This would take a lot less fittings and a lot less time to install. The down part of the subject it that for a strip that is 7.5 feet long is that it might get your sidewalk wet, or you could install them on the sidewalk side and have the road get wet. If you don't want this, I would use the Ranbird 1800 on each side about 9' apart, as you said.