On my 2013 450 it is a combination of velcro at the edges near the windows and very small Phillips screws as you remove the
panels towards the center. There may be a few visible screws on the outermost ceiling
panels. You will want to remove those outermost ceiling panels near the port and starboard windows first, then remove one at a time until you reach the center of the
boat. On your outermost panel remove any visible screws and then reach up by the window and give the panel a good pull downwards to release the velcro. Once you do this any additional screws should be visible. It's a tedious job and probably requires two people.