ideas about a copy writing competition

Hi, I just read a really entertaining thread here on WF, it was about a miracle wonder drug company running a copywriting competition. The consensus was that it was probably a scam, and no one of any worth would be likely to enter. The post got hammered by everyone, (and probably rightly so). Here is the thing though. This is very similar to an idea i had about holding a copywriting competition, (in about 6 months). Except it is for a mail out of email addresses, for a membership website. I was thinking of having a competition where every person interested in entering would provide a sales letter. This letter would be mailed to a certain number of addresses, (say 5000), and the letter with the highest return wins, (say $5K). Copy would need to be approved, (meaning not offensive or brand damaging etc). I was thinking that all entrants would receive a percentage of what their letters return, (probably 10% or so) so if your copy returns $5000 then you get $500. That way everyone receives something for their efforts, and the winner would get the most earnings along with the 5k prize money. AND bragging rights.

The obvious benefit for my business is lots of testing.

How would I orchestrate this in a way that everyone would be happy, and I would not be torn to shreds for suggesting the idea! I have built in tracking of emails so all entrants could log in and track how their copy was performing, so transparency is not an issue.

Would doing this break any forum rules or etiquette that I am not aware of? Would you guys have a crack at it, or not? Has it been done right before?

Cheers

Kurt