Hiding game clients behind other game clients doesn't help with system resources at all -- I showed this off in the Hardware Science thread almost three years ago. If what you're saying was true then you'd be able to just open up a program like Notepad, lay it on top of your game clients to "hide" them, and magically gain performance (which doesn't happen).
Either way, ISBoxer gives you the option to stack your game clients on top of each other. Other software choices may also give this option, but I haven't used anything else in five years.
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