Thanks Richard
I just filled it to the top with fuel, then opened the fuel cap when I arrived home after 10 miles, and now all seems fine.
But when I open the cap on an empty tank, there is a huge rush of air 💨 that lasts a few seconds
As long the tank doesn’t split / fail again (on the weak weld joints as some say) I’m happy. At least it doesn’t spray me with petrol anymore, the new roll over valve in a new location solved that.