For your size, you'll need one of Clark's longer hammocks, but even that might not be enough. Their longest hammocks are only nine ft long, according to the chart on their website. I have one of their NX-200, but they don't sell that anymore, you have to go with the NX-250. They are good, but those poles, for me, have a tendency to break. There are plenty of 11 ft hammocks on the market, example would be the Dream hammocks:
All the models are available in 10 ft or 11 ft. For you, I'd recommend an 11 ft, plus get one with a zipper on each side instead of only one side. That way, if one side stretches out a little, you can even it out by going in from the opposite side. At your weight, that could become a problem. I'd also recommend a double layer hammock, but if you plan on only using under quilts (as opposed to a sleeping pad), you might not need the 2nd layer.
There are other hammock builders out there that have 11 ft models, I'm just familiar with Dream Hammocks. If you want to save money, the ENO DoubleNest might meet your needs. You'll need a separate bug net to go with it. They're cheap enough (about $60?) that if hammocking doesn't work for you, you haven't invested quite so much money.