Yeah, the seat belt won't let him lay down but I put the pillow in there and it props his head up in a more comfortable position when he falls asleep and it lolls off to the side. He's fine the other way too, but it pains my neck to see it bent all crazy like that.
I have a 5-point harness in my two person trailer. My son sits in the middle and the part that comes up between his legs and over his shoulders fits well. The lap belt seems very loose to me, too, as it runs from one side to the other. In both tip-overs he was suspended by this system just fine though his helmet got the tiniest bit of use (yes, we have a new one).
I used to have an open mind but my brains kept falling out.