I really wouldn't mix them, as others have said, it's a bad idea, ask anyone who works in a tyre fitting place.
Years ago, as is probably documented on here, I had an issue with a dealer that tried to fob me off with non axel matching tyres on a nearly new car, I scanned the user manual to prove it actually says in VWs owners manual tyres should be only fitted in matching pairs. They didn't give a toss tough.
