It could still need time, but 3.8 oz or corn sugar is not excessive for five gallons, particularly not for a hefeweizen. Five or more oz wouldn't be unheard of, but, if you're using thin bottles be sure they can take the pressure if you start pushing it too far.
Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience. - C. S. Lewis, English essayist & juvenile novelist (1898 - 1963)