When inside the resistance, you can always leave and visit past levels. Go up to the surface and move to the right until you get to the pillars that regenerate when they are completely destroyed. Stand next to the wall and charge your Shield Boomerang. Jump and throw your boomerang so that you hit the top section and let yourself fall to the ground. If done correctly, your Shield Boomerang should circle you forever, as long as you do not move. Allow the system to idle for about twenty minutes in this situation to get it to the maximum level.