generator.rb

# Pretty much pseduo code
# Let's just assume you're in a loop where you are generating each post

new_data = {
  'title' => 'Some new title for this generated post post'
}
site.posts << Series::Post.new(site, site.source, index, post, new_data)

post_override.rb

module Series
  class Post < Jekyll::Post
    # index - the paginated number
    # original_post - the post which this pagination is generated from
    # new_data - overrides for YAML front-matter
    def initialize(site, base, index, original_post, new_data={})
      @site = site
      @base = base
      @dir  = File.join(original_post.url, index.to_s) # will end up at [original_post_permalink]/[index]/index.html
      @name = 'index.html'
      process(name)
      
      # Read from the original post so Jekyll doesn't freak out about this post not being on the filesystem
      read_yaml(File.join(base, File.dirname(original_post.path)), File.basename(original_post.path))
      
      # Override yaml front-matter from the original post
      self.data.merge!(new_data)
    end
  end
end