Ug I fell victim to this stupid gasket as well after installing the
Verus Engineering Fuel Starvation Door. I've removed and reseated the gasket 3+ times (with similar fuel spilling everywhere issues as devtec). I thought I got it seated correctly the last time after hammering the lock ring back in place, but I filled up last night and woke up to a small puddle of fuel on the garage floor. I've ordered two new gaskets to give it a go again, although between now and when they arrive I'll need to try to lower the fuel level in the tank to stop the leaking.
This damn gasket/fuel pump setup is pretty poorly designed - with the sprung fuel canister and tight clearances, it's pretty cumbersome. With the new gasket, I'll try to seat it in the fuel tank first before dropping in the pump canister, but when I tried it last time with the original gasket, I couldn't get the angle right with the fuel level float.