I think writing a post that includes the other post then naming the readers in the first few lines might give it to the few named persons. We have an E-mail system attached to a wallet, so I send. The problem I see is that we are leaning away from censorship and sharing with a "few" is not "public." Attaching a resource such as your SBD would work. Like a master-password posting function, instead of a posting-key function. Alongside of a mutually shared plug-in, this would allow the post to pass through the network only to those users. It has to be possible somehow...