Sorry, I only know about the one here Rabbit. Here, I don't think they would care, but I am not sure about that. They allow cheaters and shaders, so I don't think an unpadded modified buttpad should be a problem.
The target is an X cut in a board with a razor. The sighter target is whatever you want. A lot of folks use either a pointy line or a target that looks like the letter i. They line their front sight so that they can't see the leg of the I at all and then place the top of the blade at 6 o'clock on the dot. Others use a verticle pointer with a dot and two side lines to square the top of the rear sight with. The front sight is squared by the vertical line. You shoot your practice or sighter shots at the target trying to get as small a group as you can. When it is time for the first match shot, the target is put on the board with your group over an X on the board. You attempt to do everything the exact same way on every shot. If you hit the center of your sighter group every time, you should also hit the X centered under it. The sighter target is moved for each shot so that the next X is centered in the developing group. Once your target board is shot, you check it out. If you hit an X, the scoring process comes into play. You need a lead plug with a flat bottom the size of the bullet you are shooting. That slug is put in the hole and the center of the X is cut on it just like it was on the board. Closest shot to center for the match is first place. Depending on the number of participants, the number of prizes will change. They go to the butcher shop and buy meat prizes. First picks first and so on.
The matches at Friendship sound like they use the total distance from center for all scoring shots. A slug with a center point is put in the bullet hole at such matches and and the distance from the center of the slug to the center of the X minus the radius of the bullet is recorded for each shot. At the one here, only the top single shots win. To win you need to center punch an x cut with a razor on a board at 30 yards off a rest. Sounds easy, doesn't it!