Here's the post that I used for guidance: http://www.rcgroups.com/forums/showp...41&postcount=8
It's in this quite long (and unessasarily complex looking) thread: http://www.rcgroups.com/forums/showthread.php?t=1581061
So basically you just isolate one stud and snip the wire jumpers. I didn't do the stud like the picture suggests though, too much of a lash-up for my liking (though I'm sure it works ok).
What I did was removed the screws, lifted the circuit board up and filed the spigot off the stud using a small hand file. I then put a tiny 2mm long bit of heatshrink over the shank of the screw, put a fibre washer between the board and the post and another fibre washer under the head of the screw, then put the screw back in.. 15 minutes work and the circuit board is totally isolated from ground, much safer than the bodge job of removing the ground pit from the power lead.. no way should they be offered for sale in that condition.
There is a mod to increase the voltage of the PSU but I'd not recommend it. the PSU becomes unstable if you increase the voltage significantly above default.
Basically the only other mod you have to do to make your 24V PSU is to solder on the output wires (needs a good powerful iron) and short pins 6, 8 and 10 to turn the unit on. I didn't bother switching anything because you need to switch the AC supply anyway, so pointless putting a switch on the unit itself.
i did do a mod to slow the fans as they are a bit noisy as standard.