@Grace is definitely the expert in how to use tape, especially the multisize features. She literally wrote the book on it.
I approach the problem differently - I avoid using multisize files. You can use the same pattern (.val) file and have it use different measurement files. Just create a separate measurement (.vit) file for each person you want to fit. Then open valentina with the pattern and click “Measurements” in the top menu and “load individual” in the drop down menu. Enter the name of the new .vit file and those measurements will replace the first set and the pattern will be adjusted.
This will only work if you have based the points in your individual pattern on MEASUREMENTS, and not put in numeric values. If you have any problem making this work, please use this forum to upload the .val file and .vit files that you use. Someone will help. I have attached a screenshot. The red arrow points to the icon that you click to upload a file.