I'm "tooling up" right now to cast some Lee 405 hollowbase softpoints. "Tooling up" requires some wire and an assortment of pistol cases to make dippers ...not very high tech, in other words.
A .40 S&W case holds about 180 grains of alloy, and a .45 ACP case holds about 280 grains. Being as the Lee hollowbase is a nose pour (of course!) the shank metal has to be poured first, and the .45 ACP case will be the dipper for the WW metal. This will leave a nominal 120 grains of volume to be filled with the pure lead, and I'll then use a different dipper for the pure lead. I may adjust things a bit to give slightly more room for the softer metal, but these will do for a first run, anyway.
Most of my "pure lead" is derived from soft 1/8"-thick lead sheeting. However, I do smelt the stick-ons separately from the normal WW, and save them for muzzle-loaders etc where they seem to work fine.
On the question about hardness of the shank compared to the soft nose, I refer y'all again to the thread last year on "Successful Casting of Softnose Bullets....". Just do a search for "softnose" and you'll find it.
Toward the end of that thread, I described a water-jug impact test. Note that the aircooled boolit expanded RIGHT DOWN TO THE BASEBAND, which seems to imply that the shank is definitely bearing its share of responsibility. Expansion was up into the .80" area from .416". The water-dropped boolit tested retained the gascheck and its original base diameter, but still carried 300-plus grains of metal (out of 365 to start with) all the way to the sixth jug. I elected to hunt with the aircooled model, but didn't get an opportunity to use it.