Charge kit install for Goal Zero 1400

I just bought a GZ 1400 to power my Dometic fridge and other devices. I purchased the charging kit that goes directly to the battery, but they only give you 12' of cable to work with. I was thinking of cutting a hole in the bed or wall behind the cab and using a grommet to keep dirt/water out. Anyone have experience with this install or doing something similar?

Thanks!