old PC PSUs (ATX) as constant current source

Dear ng,

I've seen people using old PC ATX PSUs as a 12v lab PSU.
Now I need a 20V 5A source and thought about using 2 ATX
PSUs in series (can't use a single one with combined
+12v and -12v since all units I know have >10A for +12V
but only <1A for -12V).
I don't exactly know how the switching power supply voltage
regulation works, so would you expect this setup to work?

Thanks!
Mathias
.