Brian Tompsett gave a detailed explanation of the advantages of the trussing in his answer to the question Why do the Russians use these fence-like interstage fairings?
The gap between Stage II and Stage III in this depiction depicts the interstage trussing.
Other than the inefficiency in streamlining and drag, are there other disadvantages to the trussing compared to the interstage fairing of the Saturn V? (Fairing-the hollow metal cylinder surrounding nozzles at the bottom of the second stage in the following depiction)