Interesting. I must not be understanding something. My owners (glovebox) manual, the Factory Service manual, Factory EVTM, and TMoss' schematic all show a 20 amp fuse.
I would stick with the 20 amper because we all know that it's easy to blow the circuit protection when a dime falls into the lighter receptacle. I would not want to run an extra 120-150 Watts of power through the wiring.