I have a question. my son is 2 1/2 and 40 lbs. now out of convertable seat and into booster. booster states that you do not use lower anchor or tether. also states use of shoulder seat belt from car and removal of 5-point harness for children over 20 lbs. this scares me. a loose seat in my car w/my child in it. and he slips his hand out of the shoulder seat belt easily. i checked car seats and this was was highly rated from consumer reports. it just seems that having a little 40 lb. 2yr. old in a loose seat not attched w/grown up seat belt is a little unsafe. why can't i anchor it and use 5-point now that he is over 40 lbs. can't find any answers. please help!