I'll put in a vote for making a mess. The branches you truncate will not grow back. And I doubt that they will get much bushier. If you really need to make room, you should consider cutting back a few of the lower branches all the way to the culm, and leaving the higher ones alone. If the culms have a weeping habit, you could always just run some twine around them to straighten them up and reduce the volume of space they take up.

The twine does seem like a safer way to go. They do arch/weep. Looks nice if you don't have to try to live in the same space!

I'm fascinated that living in Z5 (Kansas?), you would buy Negra, knowing you would have to take it in to live with you in the winter. Won't it get too big for that next year? Well certainly the year after next you will have to get a bigger pot, and on and on. You will soon need a forklift and a larger house, no? Do you have a girlfriend? A wife? Is she jealous? This seasonal affair seems to me to be bamboo mania for sure, although I'm a tad manic about my Boo too, so I'm not throwing stones ...

Yes, probably mania. Black bamboo is indeed rare here in Kansas. Any trip I make to the NW coast, I bring back a bamboo or a bonsai as large as will fit in my carry-on. One of the black bamboos originated in Portland. When I found another specimen at a local garden center in a way-too-big-for-me-to-handle container several years ago, I rescued it. A few weeks ago I spent a whole day dividing it and now have way-too-many pots spread around the house. Maybe it's the empty nest I have to refill! Good thing I have a tolerant (though bemused) spouse.