[Typo3] RTE full screen width

[Cousins]

I found several references to configuration of the RTE full screen width 
using RTEfullScreenWidth= or as Kasper has stated in one thread: 
TCEFORM.[tablename].[field].RTEfullScreenWidth= xxx

But I cannot find a more explicit example of how this is used despite 
repeated searches of Typo3.org and Google. What I did find was the 
following reference:
<<Quote>>
RTEfullScreenWidth     int+/%    (applies for RTE text fields only with the 
RTE wizard configured)

The width of the RTE full screen display. If nothing is set, the whole 
width is used which means "100%". If you set an integer value, that 
indicates the pixels width.
<<end Quote>>

However it appears the RTE full screen width is set by default at 500px - I 
want to increase this to 800px - can anyone give me a full example of how 
to achieve this within a site template i.e what is the correct tablename 
and field to use?

I don't want to hard code it (assuming I can find the correct place to do 
_that_ ) as I have one preschool site where the users don't use a higher 
resolution than 800x600 yet I have another music school site where they use 
1024 and higher as they have _huge_ screens (mainly 19 and 21 inch)...

Ian