oh yeah duh, there's a gridview on the child controls (which contain the expander/dropdown)
in those... ahh
I'm setting the hight of the gridview
but not the width I think
the Sorium in the minerals panel is a compleatly seperate control and different unrelated object from the Fuel one, though there should be a "Sorium Fuel" object inside the expander it's currently not showing for other unrelated reasons that I've not yet tracked down.
You can add an issue to get the GridView to autosize properly in this case, I think it'd be really useful. It might take some hackery and fakery on Gtk, but anything is better than doing absolutely nothing