Be very careful. I would use that guide.
http://www.shadowandy.net/2012/03/asus-rt-n66u-tomatousb-firmware-flashing-guide.htm
I have used this guide previously, but can't make it upload the firmware with Asus recover utility. It keep saying that: "The wireless router is not in rescue mode", even I put it in recover mode by holding the rest button (led blinks slowly).
So, I was wondering, has this something to do with CFE being 1.0.1.2 (32K) and the fact that latest Tomato is on 64K ?
Did anybody tried to flash RT-n66u directly from Asus original firmware to latest 64k Tomato?
Highly appreciate the answers.