So after trying Nautilus, Maestro, Frontier 85 and Prosport (child on top harness height), we will probably end up with a booster for my almost 5 year old. He is about 41 lbs and 43.5 inches, narrow and slim build. The CPST at the store suggested a Clek Oobr, Recaro Vivo or Britax Parkway SG. I've read that the Parkway doesn't fit narrow kids well but I like the SG feature. This will be used in a three across which is why the combo seats didn't fit. DS's shoulders are a smidge below the top slot on his Marathon. The booster will be used with two Marathons (although I'm not sure how much longer they will last his twin sisters that are super tall) for the time being. I like the latch feature but I'm not sure how the rigid latch will fit in my 2006 Land Rover LR3 - very stiff flat seats. Any recommendations? Thanks!