If this works - that would be ideal... I'll find out next week
As stated in the article you posted, there is no bridge mode for the 3600 not can you back up any configuration. Your best option is to use the 3600 in DMZ+ mode and only attach your OpenWRT router to one of the 3600 LAN ports. Yes, this will be a bottleneck going WAN-->10/100-->oWRT-->LAN but it's livable.