Corrective Shape Key not working?

I dunno if its supposed to do this, or if I didn’t toggle an option.

Basically, I am using a shape key in my correct project - the project is a planet that has been destroyed, thus it has two halves and a central area that still has quite a bit to it despite its destruction. In order to get the look I wanted, I am using a shape key, so that the edges of the mesh I am working on don’t get modified by a displacement modifier, which is what I am using to create jagged peaks and broken mountains on the inside of the planet.

However, whenever I use the Corrective Shape Key addon, and toggle the option: create duplicate for editing, the mesh suddenly becomes very small - much smaller than teh rest of the project, which requires me to resize it. This is troublesome because I am using a shape key on multiple parts of this project, and if I have to resize each and every mesh object everytime I apply this key that it’ll become rather bothersome. In short, it throws the newly created mesh to the ‘center point’ of the project while at the same time changing its size.

Am I using the method here or do I not have an option toggled for this process?

Have you perhaps scaled the object in object mode? If yes, then this might be the problem. Try hitting Ctrl+A and applying scale, see if that works…