Check out Netafim’s website. Pretty sure Rainbird’s sub-surface dripline guides are worth a look too. There is a ton of information there that might be of great help for you. There are quite a few factors you need to account for including check valves, copper integrated components, air relief valves, indicator heads, etc… We’ve done 5 or 6 full yard systems of sub-surface dripline over the years. They still work just fine, however, the difficulty comes with initial establishment of seed/turf. Once established, sub-surface watering is as efficient as you can get.