Install tomato on Asus WL-520GC

I have two identical wireless routers that are only mildly useful with the factory firmware. I used them to establish a point-to-point connection where I didn't want to run a wire. But they would be so much more useful if I could get Tomato firmware on them. It appears that it is possible but requires a special dance as described here:

http://en.wikibooks.org/wiki/Tomato_Firmware/Installation_and_Configuration

The main problem is that I have to first downgrade the firmware to a version that allows me to put a custom firware on. That required a trip to here:

http://support.asus.com/download.aspx?SLanguage=en-us&m=wl-520gc

There I got a 2.0.0.8 version firmware. The router currently has 2.0.1.1 and that won't let me install Tomato.

Bummer with 2.0.0.8, I get the same delightful error message:

Firmware Upgrade Fail !
Firmware upgrade fail. It may result from incorrect image or error transmission. Please check the version of firmare and try again.

Next, I downloaded the earliest available English language firmware which happens to be 2.0.0.6.