I am in the same situation, though it sounds like on a smaller scale. I killed the bamboo by having a garden worker clear cut my ca. 500 sq ft of bamboo (running). Then when the sprouts came back, I sprayed a grass killer on them (bamboo is a grass), and it worked like a charm. It's taken about five years to get rid of new growths from leftover fragments. The problem, as you noted, is that bamboo is literally as hard as metal (knives and flooring are made from it, after all). The stumps left are killer: I'm always tripping on them. The only way, I'm thinking, is to use a saw that cuts metal and working from the outside-in, cut the roots to release the stump. And then pull hard. Or backhoe the whole shebang. Another detractor: bamboo seriously depletes the soil. If you're lucky enough to get rid of it, you're left with dry dust soil requiring a lot of compost. Horrible! Running bamboo is an invasive plant. Gardeners and nurseries should require permits to sell or plant it. Sure, it's pretty, but a pest. Kind of like that guy you knew in college ...

It's pretty simple. Get yourself a spade type shovel that can penetrate the soil. I have a square-nosed one that is especially useful for this. Walk along the outside boundary of where your bamboo is permitted to roam. As you go, punch the spade into the ground at least 12". Overlap your cuts to ensure you don't miss anything. If you hit anything that might be a rhizome, inspect it and cut it if necessary. Do in Summer and in Fall, or just in Fall after rhizome growth stops.

My runners send out rhizomes in the Spring. Wouldn't hurt to check twice a year. They can travel pretty far from the parent plant. I am not sure how far since mine are in a rhizome barrier. I check to see if any have gone over the top of the barrier. I am not sure how deep. Others on the site have more experience then me.

That's an interesting and complex plan. It will be somewhat effective, but not foolproof. I don't believe it's possible to "fool" rhizomes to prevent them from growing in one particular direction. I also have seen HPDE pond liner that was breached in multiple locations by rhizomes. I have rarely seen rhizomes go deeper than 12", though, so one thought I have to improve your design is to use real bamboo barrier instead of HPDE, and to install it at the backside of your raised bed so that the top side is leaning substantially back from the bamboo. That way, when the rhizomes start moving out and hit the barrier, they should slide up the barrier and pop out of the ground where you can see them and snip them off. In your Zone, clumpers may take a long time to size up and you would need quite a few for a 50' fence line, so runners are probably your best choice. If you go with runners, you'll want the hardiest ones you can get. One of the best ones for that purpose is Ph. nuda, which is hardy to about -20F. If you go to the link I have provided below, you can do a search on bamboo using various criteria to help you narrow down your list. One last thing: when growing a bamboo hedge, it is always wise to plant at least two species. You never know when bamboo might flower and die, and it's always best to have only part of your hedge fail. It might not happen in your lifetime...but you never know. You could also consider a combination of hardy runners and hardy clumpers, as some of the Fargesia species can also handle temps down to -20F. Good luck. Here is a link that might be useful: BambooWeb-Species