<p>If you need to write a letter. ONLY on new information about accomplishments and the like that your GC could/would not cover. You have applied and been deferred. It is not that you are not qualified they just have not yet gotten a feel for who they want in their class. Basically 1 in 6 deferred students gets in. We have a rather high likelyhood. Only send more if it gives major insight into how you are different.</p>