Function for itemSize makes scroll offset not able to go all the way to the bottom

[ElijahJohnson5]

Hi I am working on using the virtual list in a chat type layout and want to always have the offset start at the end of the list. However the elements are dynamically sized and I am using the itemSize as a function. This is working fin but I am not able to scroll all the way to the offset initially unless I overestimate the size of the elements and then the scroll bar gets jittery. Is there any better way to handle this?