Here, where we live in Issan, the mail is very unreliable, so I send my forms back EMS.
The way I look at it is, I can track it, I know that they received it and hey, 50 bucks a year isn't going to bankrupt me.
This is the first year my wife will receive the form. I'm thinking about sending both forms in one large envelope. I don't see why that shouldn't work?