4X4 and I believe I am looking at a pipe that is tapped into your sprinkler system from the above pic?
Whether underground or part of your drip system, I would recommend 4 hills, 2 of each kind. Since you are limited to surface area, plant 5 rhizomes in each hill. That is going to allow you to fill out each twine. Place an "underground barrier" b/w the different types(if it works but have never had to do it) and go from there. Either way, you need to think "vertically". You only have so much ground to work with, so go bulk high.
Last season, I had a three year old Chinook hill that took 4 strans of twine that were fully wrapped and that hill had 5 rhizomes to start.
Have a great time with them