I was just fiddling with this earlier today. Yesterday, I had installed the Doug Knox application, and raised the buffer to 120 minutes. I paused the TV, then went out to the garage to do some cleaning, came back after 40 some minutes to see my show playing, and the buffer lost (this is usually what happens). So apparently, Doug Knox did not work for me. I tried out the page you linked to, and after reading the comments, all I did was change the one key BackingStoreEachFileDurationSeconds in
[please note the \DVR, which is not listed in the main post, but only found in the comment section] from 300 to 900, and I verified that at least an hour and a half worth of buffer was saved. Not sure if anything over 900 works or not, but I'll see how well I do with 2 hours for the time being. Should be fine. I didn't create any new keys or edit any of the other ones listed. Just made that single edit and it worked for me. Hope this helps, if yo haven't figured it out yourself yet.