I have written numerious letters attempting to get out of infringments. Ive also spoken to a few people who work at AFP about this. This is from my personal experience, You may write a letter outlining all your cases, then, youll get a letter back in the mail saying, either pay it or goto court, where you can argue your word against the attending police officer / officers (if it was 2, your pretty much guaranteed screwed, as they will corroborate their stories).
They will prob argue, being wet conditions, you should have been being more cautious blah blah blah.
anyways, just my 2 cents,
Good luck with it.