If the parent does not change width or height then there’s no changes that would ever be needed for children. I’m guessing that your problem is that you are changing the width of a group element, and want the children to adapt?
For each element there’s a “base width” (what is specified in Hype) and a “flexible width” which represents a current value from being scaled. The base divided by flexible is used for calculating how to scale and position children. It sounds like what you want is to be able to change the flexible width and not the base width. The API only allows changing the base width. While you could change the DOM’s width (used in calculations), this will get overwritten pretty quickly by Hype and isn’t of use. In fact, I suspect that all of the values you want are getting overwritten due to the (overly) recursive nature of how Hype updates frames when flexible layout is enabled, right?
Let me know if this analysis jives with your impression, and we can move from there.