Per the instructions I was under the impression that "Current Mailing Address" was the mailing address you want all correspondence sent to (not necessarily where you are physically located), and "Residential Address" is where you are currently physically residing.
In my case I have put my wife's Canadian address for both, as I am here--with valid visitor record--visiting her throughout the process. Also for "Current country of residence" (Page 1, Question 10) I have indicated Canada.
Seems somewhat grey and now (as ever

) I am second guessing what I wrote on my form....is this incorrect?