Quite some time ago, I ran such a test. I did a reasonably careful job of it. Unfortunately, the test was run with Vandersteen speakers, not any of the models you own.

The upshot of the test was that there was no detectable difference between bi and mono-wiring until the wire got down to AWG24, at which time mono-wiring was slightly better. Since this is what would be expected, no further tests were done.