Final answer.

I got all three carseats installed. Phew! That was a job. I learned a few things:

1) Erin is, thank goodness, tall enough to go backless in her booster. The seatbelt fits her fine that way. Thank goodness she's grown so much this year. This saved my ass and my aching bank account, because the Monterrey alongside the two Radians did fit, but it was impossible for her to buckle herself in with the way the back is contoured. Without the back, she can reach around the arm rest and buckle herself in fine (even better if we duct tape the seatbelt thing to her booster so it stays in one place more easily).

2) The Peg Perego infant seat only installs well with LATCH when it comes to the HHR. The seatbelt path on that thing is the absolute worst match for Chevy seatbelts. I have no idea how we got that thing to work in our old Ford, which didn't have LATCH. However, with the current set-up, doing a LATCH install in the HHR is not an option because it has to fit 3-across, and the LATCH position takes away about 3" of seat space that I need in order to make the seats all fit. Verdict: Peg Perego seat + HHR 3-across = Totally incompatible.

3) Final answers:

In car: Backless Monterey for Erin, passenger's side outboard; Rear-facing Radian XTSL for Orren, middle; Rear-facing Radian XTSL for Chaiyo/Sirikit, driver's side outboard. The reason I put Orren in the middle is because he can climb in there himself, AND because he'll probably be going forward-facing when he turns 3, and he'll definitely need to be in the middle when he's forward-facing because it's the most protected position, so we'll put him there now so we don't have to shuffle seats too much when the time comes.

In truck: Backless Monterey for Erin, passenger's side outboard; Forward-facing Britax Marathon for Orren, middle; Peg Perego infant seat for Chaiyo/Sirikit, driver's side outboard. Again, since Orren has outgrown the rear-facing limits of his Marathon, and rides forward-facing in it, we put him in the middle so that he is more protected because he is less protected by his seat than the baby who's rear-facing. Plus, he can climb over and get into his seat himself, and it's easier to load the baby into an outboard position, AND there is a LATCH belt position on the outside seats, but not the middle, and with how poorly that infant seat installs with seatbelt in the car, I don't want to chance it in the truck. It's a super easy install with LATCH, but the seatbelt install is horrible, so we're bypassing that by using an outboard seating position for it.


When the baby outgrows the infant seat, he/she will go into the Britax Diplomat in the same position.