I'm not sure there ever was an official Dragonfly manual, as this is a homebuilt, with each builder making their own choice on how to build and which components to use. There should be a POH relevant to each specific build, unless the local authorities don't require that. For some generic manuals, I'd suggest asking on Dragonflylist on groups.io - can't post links yet, but you should be able to find it through Google.