I would like to see a few improvements in the GUI.
If idea exist and I to new to know how sorry...
1) As you drop an item to the form that the Preferred size is auto set to the size you make it on the form so if you drag adjust size it will auto change the Preferred Size Value's.
2) I also like to see a check box in Propertys Lable: Locked Size, Where if the box is checked the min/max size are auto set to the Preferred Size.
3) Seem anoying to expand the propertys then when you click on another item, have to re-expand them again, repeatedly..
I have other ideas but thats a good start..