This attached wad gives the slugs stability in flight. These sabots boast diameter mass, hollow points and deliver 10 times the hydroshock of any other sabot around. We tried them in every rifled barrel we could lay our hands on and they shot two inch groups at 100 yards out of them all. They also traveled faster than any other sabot we tested. The bottom line is to use what works best for you and what you feel comfortable with.
Most people take the advice of using whatever is comfortable.
All gauges will do the job well. As for accuracy, I see no difference in groups shot with all gauges. But remember, the bigger the mass, the higher the hydroshock and damage the slug will do upon entry. This is one time where bigger is better in my opinion. This can sometimes be a very controversial subject.