The idea of the use of skin_user is to leave the active skin in place (as any changes in that will be overwritten in an online image update) and only add screens you actually want to change to the skin_user. So the format of the skin_user would be:
Code:
<skin>
<screen name="xxxxx" etc
</screen>
<screen name="yyyyy" etc
</screen>
</skin>
In this example all screens from the active screen will be used, with the exception of the screens ' xxxxx' & 'yyyyy', which will be used from the skin_user.
The question of bbbuk was if those screens that are in the skin_user would be read from the active screen, and then amended for the contents of the screens in the skin_user; the answer to that is 'NO'.