Thanks for all that detail.
I saw on instructables where they combined the 12v rail and -12 volt rail to make a 24 v. I'm not sure how many amps that'd give as +12 is 15a and -12 is 1a. Might not be able to run fans then.
Looks like I'd be better off getting a meanwell or other such driver doesn't it?
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Since you have some extra power, you could boost them up some if you wanted. The internal Pot. SV2 will let you adjust the current. Start at 500mA and increase a little to use up the extra power. It shouldn't go much over 550mA max with this setup.