If it makes you feel any better, I didn't have any trouble with the headrest locking on the one I had. I never did get around to writing up a formal review but I guess I'll take this opportunity to add my .02 on the Apex.
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The kids’ stats for reference (at the time)
Dd1: 4.5yo, 43-44”, ~42lbs
Dd2: 10mo, 20-21lbs, ~27” at her last checkup
Limits listed in manual:
Harness
22-65lbs
34-52in
Over 1 year old
BPB
40-100lbs
43-57in
Over 1 year old
Measurements:
All without the optional “Body Pillow”
Harness slot heights
9.5”
12”
14.5”
17.25”
The bottom slots are essentially useless. Dd2 would already need the 2nd slots and she’s nowhere near the 34” minimum height.
Crotch buckle depths
4”
5.5”
7”
Seat depth is 12.5” from seat back to where it starts to curve downward.
Belt guide at the highest setting is 22.5” from seat. It is *just* below my shoulder and I’m 5’2”.
Back height is 30.5” but that might not matter much. See below.
Hip room is kind of hard to measure because the shell curves up, but I got at least 13-14”. I wear size 12 or 14 pants and I fit in it but there is no room to spare.
Weight is about 13lbs.
It is about 20” wide at the front of the seat area and about 21” wide at the side wings (the widest part). So it is only slightly smaller than the Britax Husky.
Observations:
First, the one that disappoints me the most. According to the manual the midpoint of the child’s head must not be above the top of the vehicle seat back. At first I thought that was a copy & paste error brought in from a backless booster manual, but there is a diagram in one spot that makes it clear it is no mistake. So much for that nice tall seat back. I do see where they’re coming from. The headrest is rather flimsy when fully raised. However, with the headrest down it is about as sturdy as any other adjustable back booster.
The buckle release button is very hard. Dd1 is able to unbuckle herself in every seat she’s tried lately but she’s not strong enough to release this one. I guess that’s a disadvantage if you want the child to be able to unbuckle him/herself but an advantage if you have an escape artist.
The adjuster strap is kind of short. I only had about 5” of strap left after tightening the harness on dd1 and she’s nowhere near the height or weight limits. Because of this a child approaching the harness limits might find the harness too short. Unfortunately I don’t have such a child available to try it out so that’s only a guess at this point. Also, when I let dd1 out I did the usual flip the lever and tell her to lean and she leaned far enough to get the strap wedged in the A-lock mechanism. It was very difficult to get out.
The comfort padding in the Apex is just adequate. Without the optional "Body Pillow" it is minimal. DD1 had no complaints, but she wasn't in it for an extended amount of time either.
Installation:
It installed well with both a lap only belt and a lap shoulder belt. The seat belt kept bunching up in the belt path but I think it may have been something about my car. In any case, I was able to get it tight so I was satisfied with the installation. There are no built in lock offs, but unless your vehicle is old enough to need a locking clip you won’t miss them. I don’t have a LATCH equipped vehicle available to test the LATCH installation but I don’t anticipate any issues.
There is no mention in the manual about the tether being required at any weight. However, I would strongly recommend using one at any weight, especially for the higher weights, above 40-ish lbs. There was also no mention of discontinuing use of the lower LATCH anchors and switching to a seatbelt installtion at any weight, even though though most vehicle manufacturers give a 40 or 48lb limit on the lower anchors. I would advise switching to a seatbelt installation once the weight limit on the lower anchors is reached.
Lower anchors and tether must be detached when used as a booster. This is true of most combination seats currently on the market.
Overall:
The roomy seating area and tall height means for most kids it will be the last seat they need. For families needing a higher weight harnessed seat and needing to stretch their dollar as far as possible, the Apex is a good option (provided the vehicle has proper head support). Just don't expect to get the full 65lbs out of the harness. I expect most kids will either be too tall for the harness or will run out of harness length well before reaching 65lbs. That said, if your budget can handle a little more I would recommend considering the other higher weight options available.
Pictures at
http://photobucket.com/albums/y247/cpsnisi/Cosco Safety 1st Apex/