We just got the Secure Kid 400 for DD, she is 4yr and 42lb about 41in. Last years manufacture is at Sears for $119. It fits her great, but her head slumped horribly. It seems like it would be supportive and DS has a Parkway SLX that he sleeps in just fine, the depth and angle of the head support doesn't seem much different so I think it really may depend on the child like another poster stated, not sure. DS always sleeps on the back of his head in the car with it tilted up. It would give me a headache, but he seems fine and no matter the seat that is how he ends up, except when he had the Evenflo chase, that did give him slump. Other than her infant seat DD has only been in the Costco Scenera which gave slump to the side of her head. So DH seems to think she is just used to it and her head naturally goes that way. I kept placing her head to lean on the side of the Secure kid while asleep,(which looked comfy and supportive when I did), but she just kept dropping her chin down to her chest. I think it may be because the separate adjustable head rest has her head further forward, despite the angle of the seat, than a convertible seat would. Also the sides of the head support being less angled than her previous seat could be why. In researching seats it seemed the more angled the less support and more likely for slump, however, if your child is used to turning their head to the side a less angled seat would restrict that possible causing them to slump forward instead. DH says she just has to get used to it. But we just got it today so I can't be of any more help than that. Oh, also about seat belt install, it seemed much easier to install by seatbelt than a lot of the higher priced seats I tried.