I think maybe you've run into an American v. European understanding of the cartridge. In QuickLOAD, whose drawings are based on European specs, for the most part, the rim is shown as 0.476 maximum diameter and 0.059 maximum thickness. So, if there is no agreement on the actual dimensions to use, it's pretty hard to make the shell holder to fit, much less to manufacture consistent brass.
It may be that the thing to do is email the various shell holder makers, since the
Prvi is going to be made to the European understanding of the dimensions, and say you've got a case with the rim dimensions I just gave, and ask what shell holder they recommend?