I needed 500mm x 200mm but they didn't have it so the material was wasted but it's not their fault. I had to use 2mm as 3mm is incredibly strong and 2mm would be easier to work with. A Dremel with a coarse sanding drum (not a cut-off wheel) does this best. ALWAYS wear safety goggles (not just goggles) and a respirator! Carbon fiber dust is everywhere, so use a vacuum system whenever possible. Carbon fiber dust isn't as dangerous as asbestos or quartz, but why take the risk?