G'day Where2nxt,
You should be able to connect your Solar Panel to the Anderson plug directly, as typically these are wired directly to the battery, at least in my case via a 30A fuse.
I presume your 120W panel has an inbuilt Solar Controller?
The only negative is the distance between the Solar Controller / Battery and the possible resultant voltage drop - hence efficiency may be lost depending on the voltage output.. Unfortunately they didn't use 6 B&S for me for the connection from the anderson plug through to the Battery, rather I believe it was 6mm auto. Something I may change down the track, although the Battery is rarely charged via the anderson plug now, due to the Solar Panel on the Roof.
Good luck with the charging!!
Cheers,
Glenn