Of course, the biggest concern for most people when considering extended rear facing, beside space in the vehicle and ease of use, is their baby's long legs. Obviously it looks like Amanda's legs are too long to sit in this position and she can't straighten her legs, but she isn't uncomfortable. Little kids are constantly curled up like pretzels. My girls are always trying to squeeze themselves into tiny boxes. In fact, that most uncomfortable position for them is to sit in a chair that's too big with their feet unsupported, like when they are forward facing in a car seat.
The Radian is well designed so that she can bend her legs or put them off to the sides. I think she would be a little more uncomfortable if she was still in Tali's seat with the raised sides.