Stuck OEM Crossbar Screws

Just bought a 2007 FJ Crusier with 60000+/- miles on it. Love the car but the OEM roof rack is a PITA. Fades and flakes. Trying to get the crossbars off to repaint but the top hand knobs will only back out part way and appear to be stuck on several crossbars. Penetrating oil and vice grips wouldn't budge them. Had to use a dremel tool on one to cut off - ordered more knob screws. Any ideas to get these things off or am I missing something ?