You will probably get 10 baits with a cup of plastic. you determine the amount of salt to add to get the weight and behavior you need. I would start with medium and get some softener so you can adjust as needed. Hope this helps.
Here is a mod that I did to the weighted hook mold. For heavier weights, I was able to get the bottom bouncer mold to work. Not sure it it will work for your application, but I hope it leads to a solution for you.