Just so I'm clear, you and he would be fishing together but only you would be in the tournament? If I've got that right…
You're essentially fishing "alone" the only concerns would be what advantage, if any, you gain by having that second person in the boat over someone that is truly fishing alone.

Let me know if you want to do this so I can run this by the MMA board first. I don't want to have to make this decision the morning of the tournament.

The simple solution is to have him join MMA. Seems to be good luck too, the third place winner last year joined Muskies, Inc. a couple days before the tournament.