A little more to add to this post now.
I've made a neck expander die for the project as you can see in the below photo, the expander section is polished to .423" and a 20 degree expander angle.
I've had my local gunsmith soften the bullet sizing die, polish it out to .424" and re-harden. I also made a fitted pin for the sizer die as well.
This mould is a CBE one and has tended to cast a tiny bit smaller than I wanted at .423". A 44 cal gas-check fits on the shank nicely and crimps in place tightly, as you would expect, being 6 thou oversize. A run through the sizer die just applies lube, no sizing takes place, which might be a help, might be a problem. Shooting them will soon see.
The other photo is a few sized and lubed with LBT Blue soft and ready to load and shoot.

Regards,
David.