I just finished installing a Propex heater in my Westy, added a second group 41 battery and will soon install a blue seas relay and fuse block to charge the aux battery and to isolate the remaining circuits off the main.  I have been reading links here and samba links endlessly, and one thing I don't understand is why it is advised to have fuses after the main and before the aux battery.  Isn't this overkill?
Thanks,
Finn in Taos NM
87 Westy Pooh
89 Westy Roo