My friends and I have been doing foot tournaments at this 40 acre lake since last year. We usually have 5-7 people with an entry fee of $10.
Since we all know each other, it's fairly honest.
But to avoid any conflicts of interest (family, best friend, collusion, etc.), we use a validation method that required the bass to be called in and acknowledged by all parties involved in the tournament. The bass is put on a stringer temporarily and then released after confirmation.
Usually a person who is not related is all it takes to satisfy all parties.
We haven't had to put one on a stringer yet. We all know who's word is good so it's a quick catch, weight, phone photo, and release.
Our standardized weighting system is a Berkley $20 digital scale which everyone carries.