as you have realized yourself it is not possible to resize the Overflow leader or trailer by setting heights after the layout has been finished.The instance for the trailer/leader stays fixed, scripts are not executed again and hence the subform does not resize.
I tried to find a workaround but nothing worked. The moment the leader subform content changes height it overlaps with the repeating rows.
Generally, setting heights in dynamic content after the fact can cause issues.
In a table it calculates the row height once and then keeps it for all pages.
Even if you change the field afterwards the row height stays for the follow on pages.