I've managed to get two 865l's bridged to another 865l. Two things that are strange are:
1. Once a router is placed in bridge mode, its IP address changes to 192.168.0.50, even if its current address is
192.168.1.1. While this is not all that important, it makes it difficult to find the new ip address once the router that is in router mode (with address 192.168.1.1) issues an ip address in the 192.168.1 range.
2. If you are going to attach a usb hard drive to the bridged router, you need to do so before you put it into bridge mode, as the relevant menu item isn't there in bridge mode.