Yeah grid size is what you're looking for, you don't need to make several behaviors, you can do something like:
let size = this.actor.spriteRenderer.getGridSize(); // size.width and size.height
Just a quick thing regarding your first message: let's try and have a positive attitude when encountering limitations or confusing stuff in Superpowers. Rather than affirming that there's no way to do something and voicing disappointment, you could have more neutrally asked 1) whether it was possible or if it was planned 2) explaining why it matters to you. We're all in this together and if there's a bug or missing feature, it's always possible to look into adding it.