Pointers for painting tank around the gas cap hole

On the first tank I painted, I painted too close to the hole and gas fumes ended up lifting the paint. Anyone have advise, tricks, or ways to avoid this happening? 

I do a fair amount of painting and only paint up the sides of the filler neck leaving the top surface bare metal. 
then when laquering just go over the colour coat and over the edge up to where the curve starts to level off to the top surface so that it stops before where the filler cap seal sits.
unfortunately, 1k solvent paints are not fuel proof like cellulose was so the last couple of clear coats needs to be 2k. 
Beaware 2k paint hardener contains isocyanates so you MUST have adequate protection equipment.
originally the top face of the filler neck was never painted from the factory.
original paint.

I use the widest green painters I can buy and double it up, trim tape with a scalpel at the start of the outside radius. You also need to tape the front pivot pin.

 
 

Thanks guys! 

A pro painter that hangs out on the GS Suzuki site recommends a layer of epoxy on the edge of the filler neck, covering where the paint edge stops.  This reduces the tendency of the paint edge to lift from gas fumes.