Singapore 6B or Principles of Mathematics Book 1

[Jaimejac]

My daughter is on Unit 25 of Res to Ref. She will finish Singapore 6A about the same time as she will finish the guide. I'm wondering if we should move on to Singapore 6B, which she would then finish at about Unit 9 of Rev to Rev? Or should we drop 6B and head straight into Principles of Mathematics Book 1? If we do finish 6B, would she still go into Principles of Mathematics Book 1? She's 11, so on the young side of the guide. And I saw on the HOD website that if the child finishes Singapore 6B they should head into Principles of Mathematics Book 2. But the Principles of Mathematics books say it is highly recommended to do Book 1 first. When she starts Rev to Rev it will be her "7th grade" year, so it does seem to make sense to do Book 1 for 7th grade and then Book 2 for 8th grade but I wasn't sure if we should do that if she finishes Singapore 6B. She likes the idea of skipping 6B and following the schedule for POM Book 1 in the Rev to Rev guide.