When I brought a 182RG across (with the intention of importing it) for a friend eight years ago, all that Canadian Customs seemed to care about was that the HST tax was paid, which it had been. The airplane itself was duty free, so tax only, and I was free to continue into Canada. I can't assert that it's still that way, but that's what I would expect. A customs broker or Canadian airplane sales agent should be able to confirm this for you. From distant memory, I think there are rules as to how long an American airplane can remain in Canada, though I have no idea where to research that - it's probably a customs thing. Perhaps paying the HST gets you around it...