I live in Canada and have been ordering for over 6 years from RUI, I have never had an issue before, I am in ontario.
the customs should not stop it, its for research, the officer must not know what they are doing. Just contact their CS, no need to post a thread like this, I never had an issue before myself, so this must be a random (shit happens) moment, I'm sure you will be taken care of, I always have been.