There is no problem whatsoever with kids legs touching or kicking the back of the seat. It doesn't matter if they fling them off over the side, doesn't matter if they have to sit cross-legged, doesn't matter if they put them up on the vehicle seat back (although once they're wearing shoes you might want to cover it). What matters is their neck/spine. It is so much more protected when rear-facing.
At some point, kids with long legs in shorter seat based seats can and do get too cramped. (Older Britax seats are one that comes to mind.) But many people are able to easily rear-face their kids until 3-4 years of age before that happens, even in the shortest of seat bases.
Newer seats are coming on the market every day with longer seat bases to give older toddlers/preschoolers more room to rear-face, in addition to manufacturer's giving us higher rear-facing weight limits.
It is not true that these seats with longer bases making it harder to have room in the front. Once a child can hold their own head upright, the seat no longer needs to be at the 45 degree angle required for car seats carrying newborns. An older child can be quite upright in their seat when rear-facing, and take up no more room than a forward-facing seat. That said, though, my feeling is if you (general, you) are able to manage from birth to age 1 with a rear-facing seat taking up space in the back...you can manage to age 2 or 3 also.
Queen2PrincessG, keep your dd rear-facing. She will be much safer that way! There is absolutely no question that between the age of 1 and 2 your dd will be 5 times safer rear-facing than forward-facing.
Coleen
CPST