Astral Chameleon & Flexible Signature, How do they work together? Options

[Andinel]

I'm playing a magician with the Astral Chameleon quality right now, and I'm considering taking the Flexible Signature metamagic technique at some point in the game. I was wondering which one I would apply first, though. Say if I'm a grade 4 initiate and I cast a Force 8 spell, do I:
1. Apply Astral Chameleon and then Flexible Signature, meaning that I leave no signature at all, or
2. Apply Flexible Signature first (cutting the duration to 4 hours), then Astral Chameleon, and leave a signature that lasts 2 hours?

Thanks!