Appreciate the pointers.... I ended up putting a script to restart logging and mount the usb, but I did it a little differently.
Because I don't want to restart the router... lol because of great uptime, I've just manually run the script, and it works fine.
Point /etc/rc.local to the below script, and it automatically runs at reboot.
#!/bin/sh
# log firewall drops on the outside interface, and then monitor those drops for reporting 7-31-2015
#Setup script to auto mount USB and set up firewall logging to the USB drive.
ping 192.168.1.1 -c 6
# Setup the firewall logging
iptables -N LOGGING
iptables -A INPUT -j LOGGING
iptables -I zone_wan_src_DROP -j LOG --log-prefix "IPTables-Dropped: " --log-level 4
# mount the USB stick
mount /dev/sda /mnt/usb
# Start the log over fresh
> /mnt/usb/firewallLog.log
# Lastly re-direct logging to usb stick
logread -f >> /mnt/usb/firewallLog.log &