I am going to built a box from 2x6 and a trellis here soon to make my small hop garden. I live is SW OH just north of Cincy so I figured I would play it safe and only grow Cascades, and maybe centennial. How high realistically do I need to build my trellis? I am an assistant greens keeper at a golf course so I know pretty much about horticulture and such, but grass and hops are very different so I need a little help here.