I just tell them to fill it up. When they start trying to squeeze an extra 500ml in by clicking repeatedly I below out the window that they should stop. This is usually because I don't feel like sitting there while they fart about. I almost always fill up when I'm driving further than 50km, so even if they brim it within a few minutes I've used up a bit and there's air in the system. If I'm going to be parked for a while, especially in the sun, I'll usually stop them on the fist click. I drive a diesel and it doesn't ignite all that easily, so I'm not too stressed about it randomly catching alight.
I have had a car burn out with a full tank, it was a headon, and I'd filled up (to the brim IIRC) about 20km before the accident. The fire still took quite a while to get to the back of the car and when the tank burnt it made a pretty impressive column of flame for a few minutes but they don't usually explode. The tyres exploding do make an impressive noise though.