Huh, my mixure is different. In a tall glass, I use 1 part black spiced rum, 2 parts Coke, and then a splash of lime. Very rarely I sometimes add orange bitters. That being said, your mixture is ideal, and simple. It's a true Cuba Libre especially with the Mexican Coke.
Que has hecho?!, eso ya no es un Cuba Libre si le agregas Pepsi y un montón de otras cosas que no lleva!, es algo muy simple, (Hielos, 2 honzas de Ron, Jugo de limon de Lima y la Coca Cola!)