I read an article that hypothesised that for Sx doms, the best partner would be an Sx second. Sx last would lack the intensity needed for an Sx dom. With an Sx second the only problems are that you have to pick between someone with the opposite flow to you OR someone with your ignoring as their dom. However, both of these were said to be preferable to Sx & Sx since that's too much intensity and both partners end up never being able to get enough from the other. This was an issue not found in So & So or Sp & Sp relationships.
I wanted to see / hear some examples of Sx doms together (either your own experiences or celebrities / fictional) to see how that theory would play out in reality.
Link to article.