Since you indicated in your first post that this was for 'fun", let me suggest that you choose to shoot Score, instead of Group.
The simple fact is, shooting group without moving backers is worthless, as far as the competition goes. Sure, you will have a good time, and the fun aspect is always present.
But also present is the fact that even though we are all honorable men, there is no way to certify a group unless you have a way to prove how many shots a shooter shoots.
I know this sounds crass, but I see it far too many times how, at club matches, (where backers are not used), there are "zeros", and "teen aggs" recorded. But, when it comes time to shoot a Registered Match, many of these shooters can't make two bullets touch. Or, they don't even bother to show up.
At Tomball, we shoot big time Benchrest, in that we have two Registered Group Matches that are attended by some of the best in the Country.
We also have a Club Match program where we shoot Score. The Competition is just as tough, and the scores can easilly be proved. Nobody has to go home with an ill feeling about one of his "buddies' might not having put the correct number of shots in a group.
OK, everybody, FLAME AWAY. How dare me suggest that there are shooters who would rather win something that be completely honest.
But I have said it before, and I will say it again. Shooting Group Competition without a moving backer is a useless endevour. I suppose you can do it, but just don't call it 'competition'.
Solve the problem by shooting score. The challenge is the same, and it lends its self to the "shoot for fun' format much better. Whether we admitt it or not, the word "Match" designates competition. when you compete, you want it to mean something. With score, there is no doubt that your accomplishment is for real........jackie