^I just made a big purchase from US and opted for no insurance for that very reason. Figured it gives it away and I’d be dinged.
One option I've heard though is labelling as “Made In Canada” otherwise you'd be getting taxed on an import that was originally made in Canada, which makes no sense. Or alternatively, listing in the description as “for alterations”
I still don’t fully trust customs tho, I think they’ll still take every penny they can, so I just avoided the situation with opting for no insurance.