I mount the gun, directly beside the wheel, so the wheel dips, with the nozzle, I have mounted the gun at the rear wheel too, but sometimes the side to side rocking, adds to the problem. If it’s a job, that requires me to be fussy, then I use a line stencil, or I made a line jig, using baseboards, as they flex well ( see pic below), slow, but I charge for time too. Just my 2 cents 🙂
http://i16.photobucket.com/albums/b11/shepoutside/IMG00381.jpg
