I contacted Sundtek, he said two of their tuners will work simultaneously. From a previous post, he does not recommend mixing and matching brands.
I have already bought 4x Vu+ turbo tuners, I have to therefore try to use as many of them as possible. I've just bought 2x sundtek usb tuners.
Hopefully Vu+ turbo works with Sundtek in one box to give me dual tuner capability. Otherwise I have to sell all 4x turbo tuners and buy 2x more sundtek usb tuners.
I wish I knew Vu+ turbo tuners are so poor. I assumed as I have a couple Vu+ solo2 I want to add cable tuners to, that same brand, Vu+, would be better suited.
If I knew all this before I would have just bought 4x sundtek but I had no real way of knowing. Couple of people on forums said 2x turbo tuners should work together and no reason why it shouldn't. I could not have known without buying and trying.
I bought a Solo4k last year but I didn't like it, went back to my solo2. Main reason being a couple of plugins I use were not available or didn't work properly on boxes with ARM processors. I'm looking into whether this is still the case as I still have the solo4k.
Fingers crossed, all works out with the "mix and match" as you put it.
At some point I will get the Ultimo 4k, once the price comes down a little. Although it is quite large.
Just a thought... have you tried other OEAlliance or OpenPLi images (to see if the problem is specific to Vix or whether it is more generic)? Also, have you tried to use the Vu+ image with 2 x usb Turbo tuners? Its a crap image but if it doesn't work with their own image, then log a fault with Vu+. Given my setup works and yours, using Vu+ branded equipment, does not (I'm assuming negative results); perhaps you can shame Vu+ into action.
I tried 2x vu+ turbo usb tuners on one box, with the official Vu+ image and the box just gets stuck in boot. Works with 1x turbo plugged in. So seems a vu+ driver issue. I sent a message on Vu+ official site, a bug report but received no acknowledgement nor reply since, which was many days ago. I don't know how else to get Vu+ to sort the issue out.