If you're loading a 220 at 1.2 then your weight is 264. That means you're loading the 310 at 0.8516. That's pretty high. From what I've read, you would want this canopy for high winds and nice landing areas only.
I've also heard that a lot of canopies aren't what they say they are and the size is more like a model number. Talk to the manufacturer of the canopy you want and tell them your body weight plus armor weight if you're smart enough to use it. They can add the gear weight and make a recomendation depending on the jumps you plan to do.