Stir together the paprika, salt, sugar, chili powder, chipotle powder, black pepper, garlic powder, onion powder, and cumin in a small bowl until blended. Rub the seasoning mix all over the flat iron steaks, then wrap them tightly with plastic wrap. Marinate in the refrigerator 2 to 8 hours (the longer the better).
Preheat an outdoor grill for medium-high heat, and lightly oil grate.
Cook the steaks on the preheated grill until cooked to your desired degree of doneness, about 4 minutes per side for medium. Allow the steaks to rest for 5 minutes in a warm location before slicing.
