I have successfully grown hops horizontally as well.
I grew them up about 6' then over the deck on a 3' x 3' grid made out of 2 x 4's (pre-built by the previous homeowner, it used to have a clematis growing on it, but not anymore!).
I decided to run some string on the underside of the 2 x...
I have my hops growing vertically for about 6 feet and then horizontally about 15 feet.
Almost all of the hops are dangling across the horizontal section of the vines.
Could I cut the vine near the base and leave the hop flowers dangling from the vine to dry for a few days, then harvest...