I have a possible way to handle your airbox/air intake situation.
1. Buy a second airbox cover, then vent one of them.
2. Put Dial-A-Jets in your carbs.
This way you can get more airflow when you are running them hard but switch back to the full cover when you will be in the wet/mud. The Dial-A-Jets will allow you to quickly adjust your carbs so that you can get the best performance with either cover on.
I make this suggestion only because of where I've seen you guys end up at times.
