[RPG] Is combat stamina pathfinder legal?

I Love this feat. It adds so much more flexibility to anyone who would fighting on the frontlines or midlines its insane and it manages to do it without being Overpowered.

But I just wanted to make sure, this IS pathfinder legal right? I mean i don't see why anyone would deny turning spring attack from a meh feat into an amazing one.

This is the feat in question

• Combat Stamina (Combat)

  You stop at nothing to drive your attack home.

  Prerequisite(s): Base attack bonus +1.

  Benefit(s): You gain a stamina pool. After you make an attack roll
  with a manufactured weapon, unarmed strike, or natural weapon attack
  with which you are proficient, but before the results are revealed,
  you can spend up to 5 stamina points. If you do, you gain a
  competence bonus on the attack roll equal to the number of stamina
  points you spent. If you miss with the attack, the stamina points you
  spent are still lost.

  Special: Since you have a stamina pool, you can spend your stamina
  points to use any combat tricks associated with combat feats you
  possess.

  – When you have an ability that grants you stamina points, you gain a
  stamina pool with a maximum number of stamina points equal to your
  base attack bonus + your Constitution modifier. During combat, you
  can spend stamina points from this pool to perform a combat trick,
  the specific effects of which are dictated by a combat feat you
  possess. Spending stamina points in this way is not an action, but
  you can’t do so if you are unconscious, fatigued, or exhausted. You
  can use as many combat tricks on the same action or attack as you
  like (as long as you have the stamina points to spend), but you can’t
  use the same combat trick twice within its scope. For instance, if
  you have a combat trick that affects a single attack, you can’t use
  that combat trick more than once on the same attack.