It's not illegal to import a foreign car seat into Canada and that is a fact.
Really? Then why does customs confiscate seats?
I *personally* knew one person from my baby group that was threatened to have her seat taken away when she declared it at the Blaine WA border. She was given the choice to hand it over (to them) or turn around and take it back to the store. She returned it and wasn't impressed about it! LOL
Then, there are the stories and who knows if those are true...I do know when importing strollers when my guys were smaller I've been questioned about car seats, nothing beyond that though...
Not sure I see the need for importing a seat for a small 6yo. If she is the size of a 3yo, she'll fit nicely into the Radian for several years to come. So great OP cares so much about the LO!
As for the Nutrition and bone density conversation. If she is other wise typical and eats a varied diet w/ adequate calcium and vitamin D, just b/c she is small/petite is no reason to think her bones are any less dense than anyone else her age. I'd actually argue the opposite, if she is smaller and older, her bones are more likely to be *more* stable b/c they have had more time at each stage to strengthen. Kids bones are most breakable right after a growth spurt--that's why (and how) kids can jump off a couch or wall and break a foot/ankle/arm that wouldn't have phased us (or them prior to the growth spurt). The faster you grow and the more you grow, the more likely a young person is to breaking something, as the bone(s) that have grown have yet to solidify after the growth spurt.
I also remember something about tall vs short people and spine and other bone issues/damage. Due to the increase in general Nutritional levels, people are growing taller and our bodies were not (originally) designed to support such a tall stature, as a result the skeletal support is decreased and spread out over a greater surface, with out corresponding increases or additions for muscles to support that, which for some people has caused problems. Now, add a car accident into the mix and...
I majored in Nutrition, but it's been awhile! LOL
tam