andy_lee,
What is your goal ?
Do you require to set the UCS to a solid face without selecting the face ??
Do you have difficulty selecting/choosing the face ?
Are you unable to select the face for some reason ?
If you don't select the face, how do you imagine the UCS can be set ??
More explicit details of your requirements may help to find an answer.
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added:
I have been watching this thread and noticed a lot of nasty behaviour which required deleted posts.
Please be a little nicer to each other ... we are ALL here to learn, not to play silly mean games.