So what happens when the road gets really hot and you're really going for it and then suddenly you get a brief summer downpour? That sense of balance you're used to will disappear as the two axles will have varying rates of grip depending on temperature and surface conditions. In short, you'll lose all sense of progressiveness and consistency between the front and back ends, and that's only ever going to end in tears at some point.
You may drive like a granny for all I know in which case this may apply less to you, but what happens when some idiot pulls out in front of you and you need to make an emergency manoeuvre? You simply won't know how the car is going to react on different compounds, and having 1.5tons of metal, plastic and rubber not under control is very scary.
Not particularly having a go at you mate, just more stating the reasoning why mixed tyres front and back is a bad idea waiting to happen.
Fortunately Stan does drive like a granny but as you say, its not always easy to react to other factors such as other drivers and weather. He also does a lot of miles with passengers.
4 new ones