I'm a PGY-2 at a Southern program. Having done this a couple of years ago, I'll give you my pitch on the subject. I interviewed at twelve or thirteen places, and really liked four of them, and would have been happy at my next four or five. I wrote basically a form letter that I sent to my top four places' program director, and adjusted it accordingly to the level of interest. My No. 1 letter basically said that I was placing them first (and that is where I matched) and why, as well as why I thought that I would fit there. For the next three places, I said that their program had all the qualities that I was looking for in a residency, and that I would be extremely interested in their institution and excited to train there, and that they were going to be very highly ranked on my list. I also sent a letter to my next four or five programs stating positives about their program and that I really enjoyed the visit, etc, but didn't say that I was ranking them really highly, but also didn't say that I wasn't. I didn't feel that any of this was under the table or dishonest, I really would have loved to train at any of my top programs and would have only been disapointed to open the letter and gotten three or four places. In addition to the PD letter, I sent my top four places different letters, basically stating the same things in different formats, to most if not all the attendings I interviewed with. You can come up with four or five letters and just change them around for each program/individual.
Having been on the other side of it for a couple of years, I KNOW that it makes a difference if you express your level of interest, especially if you make it individualized for the program. Our attendings want to make sure they rank people that actually want to be here, as well as those that meet our high standards. Second looks are completely optional, I can't think of anyone that has done that here that has matched. I think that if you conveyed the fact that you were very interested on interview days, and follow that up with some concrete thoughts in letter format, that will suffice.
Also, do it ASAP, my program is nearing that mysterious time when the attendings crank out their match lists and then compile it into the final one, probably in the next week or so.
Best of luck to you in your match, not all of you will make it, and I'm sorry for that, but keep your head up and keep trying (for a year or two) if you don't.
