I've been trying to get hold of 20 3" hulls myself, they are like hen's teeth. I did find some 23/4 hulls. I may have to load 12's this year.
Hal's 20 gauge 1&5/8 oz load that many of us use will fit into a Fio 2.75" hull just fine with a roll crimp. You have to leave the seal out, but I can't tell that it makes any difference.
