When my siblings and I were small enough, we would sit 5 children in the back seat of a comparably sized car occasionally. Sure it was tight, but worked until we grew old enough to start fighting over personal space, but around that time we grew too big to do that anyways.

 

2IS has this leather cover (you flip it down so it is not damaged, not up)... not sure why do you think it is easier to install? It just covers the anchors/holes... it is very hard to install it because you have to push the seat down right amount to make it fit.

with the design above, it looks a lot easier to do because hard plastic cover will guide the metal much better. I like the idea of isofix a lot but they dont make them easy to install thats for sure.

 

your second paragraph answers your first one so i don't know what else to add

and on some OTHER cars, you flip it up. and fwiw? it's painful in the gs and ls. it's better in the is. it's much easier in the gx. yes, i have been doing it

 

OP - I've got a 335i cabrio right now and my mother drives a Gen2 IS350....I'd have to say the space is ridiculously similar when I am in the same driving positions in both cars...surprisingly!

I wonder how the new tranny will be in the 3IS. I definitely don't want to be looking at a gear limiter but rather an actual shifter.

 

i would guess that flip up just covers the hole while flip down actually protects the back seat leather while you are trying to jam metal extensions into the anchors.