This is my new addon maybe you are going to like it but there was problem with t_rex size it's not bigger you can make the bosses spown egg sometimes it's not easy for make boss egg
My addon isn't cool but maybe you try it in survival world and if you are not good at downloading add-ons just press download and wait and click on the file name and wait and click on the down arrow ⬇️ and click on Minecraft and boom.