Question on Headlong Rush and Rhino Hard armor

[Troy Loney]

I taking the Headlong Rush feat and am going to buy Rhino Hide armor.

Headlong Rush [Fighter, General]

You charge your foes with immense force, heedless of your own safety.

Prerequisite: Orc or half-orc, base attack bonus +4 or higher.

Benefit: Instead of a normal charge attack, you can perform a headlong rush. A headlong rush is a charge that provokes attacks of opportunity from every foe who can reach its path, including the opponent you attack. A headlong rush otherwise functions like a charge attack (+2 attack, -2 AC, straight-line movement only), except that a successful attack deals double damage.

Rhino Hide

This +2 hide armor is made from rhinoceros hide. In addition to granting a +2 enhancement bonus to AC, it has a -1 armor check penalty and deals an additional 2d6 points of damage on any successful charge attack made by the wearer, including a mounted charge.

According to the item ability, I do not see how this should not stack. Headlong Rush is a charge attack according to the feat and Rhino Hide adds 2d6. Any thoughts on this?

[Golarion Goblin]

Your weapon damage is times two. The extra 2d6 from the armor does not double due to the feat.

[JoelF847]

Your weapon damage plus any static bonuses to damage (from strength, enhancement bonus, weapon specialization, etc.) are doubled, then the +2d6 from the rhino hide is added, since it's extra dice of damage, which is never multiplied, just like energy weapons (flaming, shocking, etc.) or sneak attack damage.

[Set]

As far as I know, bonus dice of damage, such as Sneak Attack, Skirmish, Flaming weapon property, etc. are never doubled on a Critical or similar 'doubling' properties.

If they are, it would be explicitly stated, such as with the Flaming Burst property, which concretely details what happens when the weapon scores a critical hit.