This thread has lots of pictures of older kids rear facing in a Radian.
My avi is of my older one (5.5 yo at that time) posing in the Radian. He was 35lbs at that time, so over the Canadian 30lbs RFing limit, but he still fit by height. The picture was taken just for fun.
My younger son RF'd in the Radian until 2.5 years old (exclusively) and then off/on until just recently when he hit the weight limit.
My avi is of my older one (5.5 yo at that time) posing in the Radian. He was 35lbs at that time, so over the Canadian 30lbs RFing limit, but he still fit by height. The picture was taken just for fun.
My younger son RF'd in the Radian until 2.5 years old (exclusively) and then off/on until just recently when he hit the weight limit.