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Those dins are fine for him. He can use them now no problem, and unless he gets into racing, there is no need for a din that high acording to a din chart that any shop will use.
That is technically the right answer, but if you ski aggressively and are 310 pounds I can't imagine anything other than an all metal binding holding up.
While he could easily get away with a higher din setting on his equipment, it will require him to do his own binding work.