Dear Sheri,
this is entirely expected. The improved 1.5 GB compression dictionary would make a difference only with the largest of setup payloads.
For what I see, you have already experienced "nominal" benefit from your current payload.
This is the best of what is possible with the state-of-the-art compression, presently.
In regard of compressing in a Virtual Machine environment, this will work exactly as it was a physical machine. Supposing of course, that the VM has at least 16 GB of memory when running the highest compression rate. At any rate, please consider that a Virtual Machine is Always a software emulation of physical machine. Consequently, the VM's performances will be lower than a physical machine.
Hope this helps you.
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