This is the exact opposite with me. I use light karts and rarely use the heavy ones, but I always get bombarded with shells when I'm in the lead. On the last lap of any given race, I can almost always predict what's going to happen to me, and when. First, it'll be a Blue Shell, then a lightning (or vice versa), then a couple of red shells right after each other. Then if I'm still in the lead, another blue shell will be paying another visit. This makes me hate the fact that computer characters can pick up items, because it will almost always be in their favor.