I've got a blog that supplies content to multiple MailChimp newsletters via RSS. The first newsletter works fine, but the second I'm having issues with. The issue I have is that the second newsletter has "hidden" content. This content isn't meant for wide consumption, so it doesn't appear on the frontpage, but is accessible elsewhere on the site. The snafu with this is that not all of this content is hidden, just some of it, while other pieces of content for this newsletter could overlap with the first newsletter. This obviously makes excluding everything problematic, as they could be assigned multiple categories, some of which I wouldn't want hidden.

The issue I'm running into is that I have a way to exclude this content from the frontpage, but not from the main RSS feed. I'm using WP Hide Post for this, which allows me to exclude from feed, which in turn removes it from all feeds, including the ones that feed the newsletter. I'm currently using /feed?cat=XXX to reference these feeds. Is there a way to make it so category feeds still work, just the main /feed RSS would exclude it?