Thank you for your comment but I do not agree with your cynicism :nono:. The symmetry left/right is not an issue. It stays completely symmetrical in the proposed setup.
My TAD Evolution One speaker has two sets of terminals for biwire. The crossover frequency between the coaxial mid/high unit and the bass units is 250Hz. The normal way to go is to add a second ww silver eclipse 7 for biwiring. But because the crossover frequency is as low as 250Hz perhaps it is an option to buy the new version of the silver eclipse, series 8, and use it for the mid/high terminals which does cover the main part of the frequency spectrum.:scratch2:
Also the sonic benefits of the series 8 over the 7 is according to WW website: Increased soundstage separation, resolution and dynamic impact. So that could work well. Only the series 8 has gauge 11 instead of gauge 12 for series7, so there could be a difference in sound level. That’s why I posted my question.

I never said there wouldn't be symmetry in your scenario, I was simply stating that in mine the Left/Right Symmetry would also be maintained. And in what I described you would maintain the balance intended by the original speaker designer with the high frequency / low frequency if you mix and match two different series and or gauges you would not. I wasn't being cynical I meant my idea was odd not yours. Good luck

Sorry that I misread your answer! At second reading I understand better what you were saying. Indeed symmetry is not the problem, but balance between high/low freq. could be.
I fear that my misunderstanding has something to do with the fact that English is not my native language...:redface:

If you are willing to purchase a new set of cables for high or low why not just get a biwired version of one or the other. That would be my recommendation.

You could listen until the new 8s are fully broken-in and then swap them and listen with the 7 on top and 8 on bottom and see. Let your ears be your guide. If were me, would likely do as McDaddy suggests, sell the 7s and get a pair of biwire 8s. That's what I'm saving for.

Thanks for your comments!
My experiences regarding biwiring is somewhat different from yours. Biwired cables are often just single end cables with a split at one end, not different from single ended with a jumper of the same quality as the single end cable.
This is also in agreement with the answer I got from Ivan regarding my question: “What is better: biwire cable or single ended with jumper?” Ivan’s answer: “... it really comes down to personal preference.” So not really SQ issue!
It is quite a different ball game when using 2 sets of speaker cables. That is also what Ivan tried and posted about post on 12-24-2016: “TAD R1's get Dual runs of WW Silver Eclipse 7 speaker cables” . He reported: “My initial listening impressions are quite favorable. I like what I'm hearing, more dynamics and detail. Both Rich & Mitch also concur, this was a worthwhile upgrade.”
This is also my experience when I did an experiment using my old MIT M-770 cable for Low in combination with my WW Silver Eclipse 7 for High on my TAD-E1. Even with this somewhat uneven combination the increase in detail and dynamics was impressive and with also a much larger soundstage!
So I am very curious what 2 sets of WW can bring and also if combination with version 8 could be used.

To each his own I guess. My personal experience is the opposite and I noticed a marked improvement in going from 2 speaker cables to a biwired version. Having said that, I made a significant jump from my prior Kimber cables to Wireworld Gold’s so that plays into it as well.