I was in two minds on whether to ask wildone to delete this post, why?
This is a highly dangerous procedure to go messing inside a power supply while it is on and running even with a minimal knowledge of electronics this is a foolish thing to do without the proper test equipment. Using a piece of software to test your end results is also foolhardy.
I would suggest extreme caution if you are interested in this "mod" ... PCReview will not attend your funeral.
A simple solution to this "problem" would be to do your homework on which PSU to purchase to fulfil your needs.
Yes ,muck is right ,do not attempt this if you do not have some knowledge of the internal workings of a power supply ,and if you do it ,DO NOT LEAVE IT PLUGGED IN!! ,you just adjust a bit ,then test to see what its gotton you,I will have screen shot in about 8-9 hours when I get home from work to show xactly what it does get you.