After a further check of the situation (and looking at mowers of other brands that do not have the issue) I figured out my issue with my 2014 Simplicity Regent EX with the 22 hp. Briggs. The issue is that the bottom of the tank is about a quarter inch from the bottom of the fill neck so that gasoline will hardly go in. The fill neck is off to the side of the main part of the tank and that part of the tank is just too shallow. I think to really fix the issue it would be necessary to install a redesigned tank.