I have been subtracting 20% from the length and quanity of whatever my brother catches for so long it's now second nature. It really doesn't matter to either of us who got the biggest or most. Regardless of the actual results every trip ends with one of us saying "this is the best day of fishing I ever had".
Now we are very competitive when it come to the Man Points System, you know, loose a fish because of a bad knot 10 points off, break a rod 20 points off, run out of beer or forget the coffee on an overnighter 100 points off. Of course all this is in jest and quickly forgotten in time for the next trip.