I wouldn't clear customs at YVR nor would I go near yVR airspace for that matter, best place to clear customs is czbb boundary bay.
There is a number you can get to call , you tell the customs what time you are arriving. They will document your aircraft ID, your name by phone, but probably wont be at the airport when you arrive unless they suspect you have something on you.
I have done it twice and neither times did the officer actually show up tot eh air terminal.
