I am planning on planting my 1st year hop garden in the next 2 weeks and wanted to run my plan by some more knowledgeable hop growers. I am going to be building a 8'x4'x12" cedar box for my yard which is going to be sitting on top of some existing soil which I have tilled. I am going to be dedicating half the box (4 feet) to growing Cascade hops and the other half to 4 tomato plants. I was planning on planting 3 Cascade Rhizomes planted 16" apart and when they start growing up running twine to an eye bolts 15 feet up on the side of my house. I was planning on putting 16 cubic feet of top soil in the box (6" high), but wanted to know at what depth I should plant the rhizomes? Any other suggestions? Thanks!