Users would get torqued out of wack pretty quickly and complain if their personal preferences changed all the time. <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" /> Again that's the power of threads - everyone can customize their own experience.
You can update everyone with a query though:
UPDATE w3t_Users
SET U_TextCols = 'xxxx',
U_TextRows = 'yyyy'
As per customizing things, you might wish to share this document with your users.... it's setup so that you can cust and paste to your site.
http://www.threadsdev.com/forum/showflat.php/Cat/0/Number/55195