Depends on his speed, not weight. The assumption that anyone who gains weight is appreciably slowed down is erroneous. Increased weight can involve increased muscle tone, which can positively impact on speed. Love those big, heavy wide-outs that can move. Of course, increased weight can slow one down, but that's not always the case.
Kaufmann can catch the ball. Though he's never been the speediest wide receiver, the weight will not impact on his ability to catch a pass. Could be interesting, especially match-up wise.