The higher the fat content of your beef, the more it will shrink when baked.
If you’re using very lean beef (like 93/7), add 2 tablespoons of water to the seasonings so the resulting patties will be juicier.
You could also slice the cooked beef into full-size burger patties. I go with sliders because it's easier to portion them for my kids. And because they're cute. The sliders, I mean. And the kids.