Can you uses Heighten Spell with Signature Spell? So when you convert a spell to your Signature Spell can you get the benifit of the Heighten Spell feat if you have it.
I don't see why you can't Metamagic a Signature spell... Clerics can do it with their Healing/Harm spells. Only, like other spontaneous Metamagicked spells, it would take a full round action to cast it, and use a higher spell slot.