Is it have control panel as Asus firmware?
Openwrt or Custom Firmware on asus? - http://wl700ge.hezik.nl/ - Http://wl700g.homelinux.net
My ASUS collection: WL500gp(80GB usb-hdd - Running OpenWrt Kamikaze 7.09) | WL700gE(250GB - Running OpenWrt Kamikaze 8.09rc1)
switching to HDD root should be done earlier that in done. otherwise all ipk installed modules will be not launched, and user will have to take care to initialize them.
mutch better aproach is Oleg's firware example - set NVRAM variable for HDD boot.