@ northsea
Why do you wanna cast in a rigid hook ?
Seems to me , that the loose connection between hookeye and cast-in wire hook(inside of the plastic bait)on the original lure is partly responsible for its outstanding flexible action displayed in that video .
And why do you want to take cupped metal lips instead of plane ones like the original lure obviously has ?
The cupped ones might only be harder to be fit repeatively into your mold , would even be tricky with plane ones .
I have made a similar mold before , to cast a leadweight onto a plane piece of sheet metal , but made it from aluminium , by routing .
Don't have any experience with molds of cement and plaster , but I am not quite sure , whether they'd be accurate enough to shape a slender cavity to accommodate that spoon lip ????
Well , just a few thoughts......!
good luck , diemai