You game the Scottish system by having different parties competing for the constituency vote and the list vote. This works particularly well for the SNP, which wins nearly all of the constituency seats, but the principle applies also to Pro UK parties. This is the logic behind All for Unity. The way to maximise the Pro UK vote is for Pro UK voters to choose whichever of the Lib Dems, Labour or Conservatives are most likely to win in each constituency and then vote for someone else in the list.
https://vk.com/video503532632_456240781
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