For what it's worth I've never had issues ordering anything from the US, though liquids are always a potential problem. However I don't believe hardware has been refused for any reasons with the exception of cartomizers, as from what I've heard they may hold them due to the chances that there may be "traces of nicotine" in them (according to HC). Yeah, that's a load, but that's what I've heard. On the other hand border refusal seems to be pretty rare -- they can only check so many packages that cross the border, after all -- but it's always a concern.
If you're worried, Happy Vaper in Ontario carries the Bloog MaxxFusion, and Best Vapour in Alberta carries the Volt, both of which are pretty much the same as the G6.