I've been shooting softnose cast for about 6 years now & they really seem to be working great, we've taken deer, elk & 3 moose with them using sixguns, none were shot more than once. Wish I would have known about them when I handgun hunted in Africa.
I use the Ross Seyfried method but have a dipper in each hand at the same time, my small 380 case carries the pure lead & my regular dipper has the WW alloy, that I water quench . Pouring the WW alloy over the pure lead from 1/2" away doesn't cause me any concern about mixing. My mould is sitting level on a piece of steel plate between the 2 lead pots.
Keep the "seam" above the ogive on your slugs & you won't have any accuracy problems & you can't pull the 2 pieces apart, I've tried it. As Lloyd mentioned, if the nose shears off, big deal, the works already been done just like John Nosler designed his bullets.
Dick