Playbooks

Weak I Pro puts the fullback in a traditional I formation stack behind the quarterback with the halfback aligned deep, then splits a tight end and two wide receivers to create a balanced 21 personnel look that leans its strength away from the tight end. Unlike Weak I Twin TE or the tighter bunched sets in the formation, Pro gives you a true split end on the weak side and a flanker off the tight end, which means you get legitimate outside leverage on both sides of the ball instead of one crowded strong side. That alignment matters because defenses reading 21 personnel almost always drop into base 4-3 or a single high shell, and Pro forces them to defend the full field width with linebackers who cannot run with a slot receiver.
Read the safety count pre-snap. Single high means Skinny Posts or Frogs Skinny Posts is live down the seam, two high means work Counter F and HB Gut into the light box.
Set up PA Boot after you have established Counter F and HB Gut in the same game, otherwise the flat defender will not commit to the run fake and the rollout is a coverage sack.
Motion the flanker across pre-snap to identify man or zone. If the corner travels, check to Quick Slants and let the split end win on the isolated side.
Hot route the fullback on a flat or a wheel out of PA F Slide when you see a linebacker matched up in man. That is a free mismatch every time.
On third and short, stay in this set rather than shifting to a spread look. HB Gut with the fullback lead is efficient, and the defense usually stays in base personnel expecting the same call.