Like boots said, try the flex tubing ( swing pipe).
Dependent on the zone pressure / available water flow that tubing should be able to handle more then one head and hanadle the 8'.
Yes, it's not good to go far with swing pipe because of the high amount of friction loss... but if the pipe can handle the extra pressure loss and flow. It's not going to kill the system by doing it this way..
I don't ever swing tee more then once, even if the flow is good enough.. It's a hack job
Take off the sprinkler head from the flex tubing, turn on the zone. If other sprays heads are semi- popping up and say.. water is shooting out of the swing pipe at least 10' away. Then your fine..
If you want to go the pvc way
All of these are okay ways to tap into your existing pvc
Although i prefer the
telescopic slip fix , Grab a
Tee fitting , a
90 and run pvc down to your sprinkler head.. Install a
sprinkler 90 with a
swing 90 , attach the pipe to your head and your good to go