I've just tried to use Slide In with related posts. On my site it seemed to have problems with Floating Social (appear s behind it), but since it covers the same area, I just disabled Floating Social.
I really like the idea of related, but
1) It seems to not find posts with the same tags even when there are many.
2) I then switched to find related on categories, which is not as nice as tags. But it also shows the same post as the user is viewing, which is fairly weird.
3) The Google+1 symbol floats through the screen when the post start (on the latest Chrome, Windows 7)
The site is stgsys.net (I tried setting it on the discussion editor - but it can't find Slide In the list of installed plugins)