Measure twice, cut once. Knocked out most of the hole with a cut off wheel. Then finished it with a carbide burr on a die grinder and a file. Took probably 30 mins from start to finish, layout to a good hole with the neck in it. 
Added the stainless mesh to the bottom of the filler neck. The longer than needed neck will help to reduce splashing up into the vent and will also help to keep crap out of the gas. Fly's, ear plugs, anything you can think of. Never hurts to have as many layer of filters as possible, because being stuck along side the road sucks because the gas line is plugged.
