Impact and Double weapons

[Dread Knight]

The Double special feature on weapons say that you can use it as if fighting with two weapons just as if you were fighting with a one-handed and a light weapon.

Impact says that it can be placed on melee weapons that are not light weapons.

So can you put Impact on both parts of a double weapon and have them work since a double isn't really a light weapon?

Does the side you use as a light weapon for TWF no longer benefit from the enchantment since you're using it as one?

Or can the other side just not be enchanted with Impact?

[Archaeik]

I'd say "used as" does not constitute the offhand weapon becoming light.

I can potentially see a very strict GM taking issue with this, but that does not make such a ruling rules accurate.

Double weapons comes with benefits and drawbacks, generally one benefit is effectively wielding 2 1H weapons without the additional penalty normally applied for doing so.

With the proliferation of material, there are a number of double weapons that use what would otherwise be a light weapon for one or both ends.

I'd say you should get the benefit of Impact regardless whether or not the attack is offhand, provided that the actual weapon it is applied to would not otherwise be considered light.

[Durngrun Stonebreaker]

Yes, double weapons are two handed weapons. (Well I think there is one one handed double weapon). So you should be able to enchant both ends.