Is this safe? My son has been riding the special needs bus all year (a "short" school bus, not a van), but recently they've been putting him in a backless booster. He definitely fits the seat belt better with the booster (he's very small and slim even for a kindergartener) but I saw a comment elsewhere that seemed to imply that using a booster without a shoulder belt is worse than sitting in just the lap belt without a booster. Is that right?