The Problem with Sock Wars

I got the Socks-of-Doom-in-Progress for my next victim, and have discovered yet another troubling fact of Sock Wars -- it's hard to knit like another person.

I received in the mail one completed sock, and a few inches of its mate. Tension was really loose on the completed sock (looser than the pattern calls for), and I had to go up three needle sizes to try to match. Nevertheless, when I was complete, this was the result:

My sock, the one on the left, is clearly smaller than the original sock.

I'm not sure what to do. This is a sloppy kill, and I think it would be bad form to just send these on and call myself the victor. I think I should try to knit a third sock, maybe unraveling the first sock to create a better fit? [Update from later in the evening: that's what I've done, begun working on a third sock out of this yarn so that my victim will get two socks of the same size.]

The yarn, by the way, is Lion Brand Magic Stripes, superwash wool and nylon, doubled. It horrified me when I first saw it, but it ultimately wasn't too bad. I had to do some fiddling, however, to try and make the self-striping do its work. In this picture you can see several places where I had to adjust one strand to get the color to match up on the other strand.