The best practice is NEVER mix tire treads.
Moreover, the vehicle is predominantly a front wheel drive vehicle…. why put used on the front and new on the rear??

 

I asked my tire shop guy this same question some years ago. He told me that best practice when your tires are of different age is to put the better tires on the rear. In a situation where the driver loses control over snow, ice, or rain, the driver can adjust the position of the front tires using the steering wheel. But the rear tires are stationary and cannot be adjusted by the driver to compensate for any hazards, so it's more important that the rear tires retain their grip on their own. And that's why the better tires go on the rear.

 

Thanks for the information. Best of luck to you.

 

Yes.

Also in light of the fact that the rear drive is only rarely engaged on dry pavement (where it can't slip), I'd be more comfortable with mis-matched diameters between front and rear. If you're on mud or snow, there will be plenty of slip anyway.