Your training with your armor lets you increase its effectiveness even further.
Prerequisites: BAB +8, Armor Focus
When wearing armor in the weight class selected for Armor Focus, you gain another +1 armor bonus to your AC that stacks with the bonus from Armor Focus. You also reduce the ACP by 1 after any other adjustments are made (such as the -3 ACP from armor made of mithral)
Special: You may take this feat multiple times. Its effects do not stack. Each time you take this feat, you apply it to a different weight class of armor.