You need to open the castspellwindow.xml file with note pad or word pad. There are probably other programs for it but i dont know wat they are
In it you should see lines that look like
<InvSlot item="CS_FACE">
and
<InvSlot item="CS_ARMS">
These are the sections that define and place those inv slots
Youll need to rename these to something you can recognize if you decide to change them later. Also decided where you want each replacement piece to go
A few lines dwn from those you will see a line that says
<EQType>3</EQType>
With a different number for each, youll need to replace that number under each one with the correct one for shoulders and wrist.
Wrist is 10
Shoulder is 6
Make sure you change the right numbers in the right area otherwise you wont get what you want.
Finally youll have to change this line
<Pieces>CS_ARMS</Pieces>
and
<Pieces>CS_FACE</Pieces>
to what ever you renamed the first lines to. If the names are exact the ui wont recognize the window piece and it wont appear.
That should do it.