Penetrating Strike + Greater True Death Crystal

[EmperorSarda]

Question, for rogues who take Penetrating Strike, they can do half their sneak attack damage as holy to undead, since undead are immune to sneak attacks? But if that rogue has a weapon with a Greater Truedeath Crystal on it that allows sneak attacks on undead, does that increase the sneak attack damage, so that if the rogue normally sneak attacks at say 6d6 damage, he sneak attacks undead for 9d6 now?

Also, does the same hold true for Death's Ruin in Complete Champion?

[The Viscount]

Penetrating strike does not deal holy damage, nor does Death's Ruin. Unfortunately due to their wording, neither one will stack with normal SA, as Penetrating Strike only works against a creature immune to your sneak attack, which an undead would not be due to greater truedeath crystal. Death's Ruin states that you only deal one-half your normal SA, so it would actually result in 3d6 if you had the greater truedeath crystal. Sorry.