In our cars with tiny foot-boxes, most often it's big toe-little toe rather than heel-toe.
On most Spyders, the relation of the brake pedal when on the brakes to the throttle is exactly adjacent and maybe just behind the brake. It is such that you can keep even pressure or modulate the brake whilst rolling your ankle and blipping the throttle with your little toes. My Cayman works that way too.
I brake with about two-thirds of my foot letting my little toes hang near the gas. Don't wear big clod work boots when attempting this.