Question about wire gauges in to P1900

Every time I think I have my plan set I come up with new questions.... :wacko:

I have decided to use my fusebox to power my P1900 - mostly cuz I'm too much of a p__sy to mess with my battery but also so that my dealership can't whine that I've changed my electrical system.

Consequently I bought two Add-a-circuit components (similar to http://www.amazon.com/Pico-0956PT-Mi...=pd_sbs_auto_2). The plan:

* connect a switched source with valet switch and a 10A fuse (max the Add a circuit will allow)

* connect a constant source with a 10A fuse

* run 10awg wire for both connections above from fuse box to trunk

* connect to yellow and red wires of P1900

* ground P1900 to chassis in trunk using 10awg wire


Does all of this make sense? I've read a couple of things saying that I need a fuse when going from a bigger wire to a smaller one... so would I need a fuse in the trunk where the 10awg wire meets the P1900 14awg wire?

Thanks as always...

Matt