:) DH figures one envelope, both forms folded together so they are both sure to be removed from the envelope at the same time. I would have folded them separately so that whoever opens it would see there were two distinct forms with different names on them. I think maybe DH's way would be better, though, so one doesn't get left in the envelope, or just use separate envelopes entirely.
I never expected a reply from the IRS, I was thinking registered mail just so I would have proof on my end that it was sent.
Thanks, guys. I was just curious about how other people were dealing with this.