Hey there Eric,
As a shop owner here in Canada, alot of my stock I get out of the US, as well as Asia and Europe.
Although the shipping is usually more expensive, all Canada Customs will charge you with for plastic kits is the HST. And then its really a hit or miss venture as to whether Canada Customs will even charge you the tax on it or not. It all depends on their mood that day.
There are basically 3 flavors of a Canada Customs check...
1. The ignor it and allow it to pass unscathed
2. They charge you the HST on the reported amount on the customs sticker or paperwork, oh and then by the way, charge you a $5 handling fee for doing their job.
3. They actually open the parcel to make sure that the amount on the customs sticker matches that inside the parcel, in which case they will then charge you the HST on the higher of the 2 amounts, and then charge you an $8 handling fee ($3 for having to open it) for doing their job.
And as I said, there is no semblance of what they will do, you might have a box come through now unscathed, next time it might be hit with HST, then you might not get hit for awhile, just depends on their mood.
Of course, you could always avoid all of that, and buy your stuff from a Canadian Mail order shop like myself. Feel free to check out my site.
Elm City Hobbies