This has been asked recently in another thread, but the response was a bit confusing. So I'm posting here to ask for clarification.
From the first thread:
VoceNoctum wrote, "First question: Can you only add the powers as extra's to another power if they're listed?"
You responded, "If it fits the character concept and the GM allows it, then yes."
Now naturally, a GM can override or change any rule. But what's the official rule? By the book, are you limited to only to those extras listed, or can any power be used as any extra?
The fact that some pre-generated characters have Super Abilities stacked as extras makes the situation more clouded. Is this allowed, or denied, anywhere in the rules?