Uth is 1680x1050 native, so you wouldn't have to change any of the values to get it to work.
Different authors put information at the start of the file, so it may not always be line 22.
In order for the toolbar to be placed properly, you'll need to modify the X and Y position manually in the SkinDefinition.xml file. The line you'll need to modify is the following line:
<Element ID="ToolbarField" X="..." Y="..." Width="1024" Height="144">
The rules for calculating the values are:
X = (Resolution Width - 1024) / 2
Y = Resolution Height - 135
That is the Line you have to edit to place it in the center of your screen. There are UIs that have you place it in different locations, so the calculations would be different.