...My concern is the niggardly amount of lube the grooves accept...
It has been observed by shooting cast lead bullets into snow and then recovering them that almost all the lube is still intact within the grooves no matter how hot the load was. Therefore, it has been opined by many bullet casters that a very small amount of lube is sufficient even for the hottest loads. Some casters will only lube the last groove in multi-grooved bullet designs.
I would suggest that you shoot the bullets and see if they perform without leading and not worry about how much lube they hold.