Sorry for the ignorance, but if the forum posts require login to access then you won't be able to use SingleFile, right?
Also, how is the quality of the output generated compared to a .pdf? I'm used to print PDFs from chrome for articles that I want to save, but the layout can become awkward sometimes, and navigation bars can appear several times and hide portions of the text.
I like this feature from chrome, but it's not consistently reliable.