Adding a window/inspection hole in Quicktime or similar scattershield.

My suggestion would be to get in touch with the safety person, with the sanctioning body where you may be racing. See what race close to you that he or she will be attending and go meet them. In my experience, the IHRA safety people are top drawer and answer your questions not to mention they will show you in the rules. Unfortunately the rule books are in CD form theses days rather than printed matter.