It was surprisingly easy, and maybe everyone knows how now, but just in case...
First, I read all the threads about using the Firewire connection and it simply didn't work for me. Being both desperate and simple-minded, I finally simply used the Component Video outputs on the back of the DCT6412 and connected them to the component inputs on the front of my Panasonic DMR-EZ28. I played a 2-hr HD show on the DCT6412, hit the record button on the Panny and it recorded nicely, thank you very much. I was pretty impressed with the final quality, too.
The shows I've archived so far are not premium channels so they're not copy-protected. I simply run out of room on the hard drive once in awhile and need to move stuff off it onto rewritable discs in the Panny.
Having looked for a long time to figure this out (doh - head slap), I thought I'd share.