996 petrol tank expanding

[nickster]

I have a black car,so admit it may suffer in the heat a bit more than others - but wondered if anyone else had any experiences with petrol spewing out once you've
filled up.On a hot day a few weeks back,I lost about 4 litres.I remember this happening on a 1967 911 once,on a hot day years ago.Is this some sort of design feature?Does everyone just dare fill up 2 thirds if the weathers good.

cheers