it might also be factor of what guage strings, the heavier ones being less likely to go sharp,
and how much tension you are using with the capo. seems like you just want enough to hold the strings down.
i get the most consistent and music feedback from my 335 copy, so besides volume and gain, i would say a semi-hollow is a big help. i also find that certain guitars like/dislike to feedback on certain notes.
Initially, I would say Canada Post pays as it was delivered to them. But since USPS insured it, perhaps they pay you and then Canada Post settles with them?
(in other words, hmmm). I suppose I would check the legalease on the USPS website.
Since you will be travelling back and forth, you could consider purchasing a guitar in Montreal and leaving it in a locker (perhaps at the airport or maybe even the hotel will store it for you), and then picking it up when you return.