Hi everyone!
I flagpoled and landed in Canada two days ago!!
My mother-in-law was kind enough to drive my wife and I across the US border and back.
I was so worried about bringing extra documentation to show CBSA when I landed in Canada (in case I got grilled for whatever reason) that I forgot I needed an I-94 form in addition to my US tourist visa in order to enter the US. The US border agents were unusually nice and said "don't worry, we'll give you an I-94 form in secondary" so all three of us got pulled into secondary because of me. The agent at the secondary office who filled out the I-94 for me was also super nice, which was weird for me as I am used to being scrutinized by US immigration/customs agents. The last time I traveled to the US was 6 years ago and the US immigration agent at the airport insinuated that I had a fake/stolen passport and when I asked if anything was wrong he got very mouthy, but let me through anyway.
We went to a supermarket in Blaine and six 12-can cases of pop later (they had so many varieties of pop there... holy cow), we headed back to Canada, told the CBSA officer I was landing and were sent to secondary. I got asked a few questions and sent to sit down to wait for the CBSA officer to fill out paperwork, which was the longest wait ever - at one point there were 3 other officers helping him so I guess maybe he wasn't familiar with landing procedures? Got called back to the counter, signed the COPR, was warned not to go outside Canada and the US before receiving my PR card in the mail, was handed a really outdated 'things to do after you land' guide of sorts, and the officer said "Welcome to Canada."
Done!