I'd have to check for certain, but AFAIK, it had toughened transparencies, and, of course, the thicker, heavier 'Panzerglas' armoured shield for the pilot's head. I also seem to recall that the framework needed to be thicker/heavier to prevent excessive flexing and distortion. With all the extra metal work, it's little wonder the 'Erla' hood was introduced. Would have been better still if a hood similar to that used on the Avia had been available, but I think the facilities for 'blowing' Perspex where perhaps not available, or not a priority.