Robin, 

   The 0.1 limit is in arsec. So you should be able to do better if 
Chris gives you time for more tests. I wouldn't make a new version 
with the figures you give. 

   Of course, if Chris doesn't give more time, then you'll have to 
use the final values, but then you'll have 0.3 arcsec movement due
to derotator errors. 

   In any case you need a final check of the new version. I'd do that 
by a repeat test. 

Regards,
Frank