Is there any way to increase the enhancement bonus on a Phantom Blade's phantom weapon beyond the amount given by standard phantom weapon progression, even just temporarily? Unlike a Bladebound Magus' black blade, there's no option to spend a point to increase the weapon's enhancement bonus (though it's nice that the Phantom Blade has a wider selection of special weapon properties to pick from).
I'm asking mostly because I'm worried about DR being a big issue for the archetype, so if someone knows another way to effectively deal with DR that would also be helpful.