K.R.
I read other responses. My son was switched to the Britax Marathon at about 5 months. REAR-FACING. People are telling you no cause should be rear facing, but my full size does go rear facing?? I agree.. the carrier was way to heavy. You are fine to do that as long as you keep rear facing for 1 year,which I think you know. The 2 yr old.. NO.. must stay in full-size. There have been so many news reports,etc about this. Keep them in a 5 pt harness as long you can. My marathon goes up to 60 or 80 pounds? I forget.. my son only 16 months, so not there yet. But the Marathon ranks pretty high for safety. I did my research before buying. Best of luck!