For those who use the TDC, have you check your VISA bill? I found they didn't charge me all the time (we used TDC all the times in the 1st year). I ask my friend to check and he said the same as well.
I checked with Point Roberts, Blaine and Pacific Crossing, all of the Canadian custom said I can do verbal declaration. I think it's a good idea because if you fill the TDC, you get taxed for everything.
I rather make a second trip to US as well if I know I am over by a bit. It's is better to buy $200/pp each time than $300/pp.
Still, with the amount of traffic back/to US, I don't think the CBSA has that much man power to tax even 20% of them.
well, like I said, crossing border is always a test on your luck in whether you got tax or not.
Having 4 people may not always help. However, I found that when having a cute dog with us definitely helped. I heard a baby will help crossing border too.