Where are you located? 7b covers a large area. How much rainfall do you receive annually?

Kt

I dunno. I'm in Maryland.

I can't say for sure, in your area, but maybe a mountain bamboo...one of the Fargesias or Chusqueas.

Also, runner's should survive in your area, although being that far north, they probably won't reach their full potential.
Phyllostachys has several varieties that get quite large but might not get as strong as you like. The tropical clumpers(Guaduas, Dendrocalamus, Gigantochloas, etc.) are the thickest of the large bamboos but they won't do well in your area.

If you want really large boo, look into Phyllostachys bambusoides(over a dozen varieties), P. edulis, P. Vivax, P. rubromarginata, and P. viridis, among a few others.

This will get you started, but someone else closer to your area might be more informed then I.

Click Here For Bamboo Speciessize>

Good Luck.

Kt

I know that black bamboo grows very well here. Does that help?

?? But which bamboos have the hardest wood?

Where I live, we have almost 100 degrees Fahrenheit every day in the summer, alternating bouts of drought and humidity, cold, snowy winters (seems less cold and less snowy every year).