I think he means you can't load a vsti under a vsti only vst's, you need to be able to send the midi out of a vsti into another. So say I want to send the midi out of RealGuitar to Kontakt.
I managed to load a vsti under it by renaming a vsti to an existing vst (fooling it), then it loaded but didn't receive the midi from the vsti above it.

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