A similar question was asked here but the answer refers to something called QL Stephen, which only claims to preview files with no extension. I need something that will show previews of files with extensions that are unknown to the Finder. They are all plain-text files. And, it needs to run on Lion (10.7).
To clarify: I'm not looking for a default QL for any unknown extension, but rather for one that will preview certain specific extensions (e.g., .sps, .fort) as plain text.