I don't believe that one's been done before - sounds interesting! I don't think the presentation needs to be in ad form. People could present it as a tech spec or just a nice picture, but I think that should be up to the individual. The challenge itself, to me, should just be modding your item to make it fit Trek.
BTW, several months back, I wanted to keep a running tally of past challenges with each new one, but it looks like October
was the last time it was included.