Not sure if this info will help or not b/c its a slightly different situation, but here are some notes from a guy who brought a passat syncro shell over.
well i planned on dropping the back part of the shell at the junkyard, but got there too late
so i decided to cross the border like that, had no problems, thank god
the thing is that the Passat is a Non-Conforming Vehicle according to the NHSTA (like a Rallye Golf) so you cant import it unless you go through a Registered Importer (AKA Ripoff Artist)
so i figured cutting it would render it unuasable as a shell and it worked
since i could never Title or Register it in the US the shell was useless to me anyways
FYI the Duty Free limit on car pats from Canada is $800 USD
http://forums.vwvortex.com/zerothread?id=1687747