Have you found a private tracker that works well for documentaries? I've tried TorrentLeech, FileList, MVGroup, and usenet so far, but my to-find list still has several releases I have yet to find in 1080p (despite most such documentaries having released since 2010). MVGroup is the best tracker for documentaries I've found so far, but they tend to upload lots of documentaries a tier below their optimal resolutions (ie 2160p documentaries in 1080p and 1080p documentaries in 720p).