As I mentioned earlier in this thread, I lost some friends and colleagues in an F-28 crash in 1989. After the accident a study was done to ascertain how critical contamination was on the F-28 wing. As I recall a single grain of sand in one cm2 (6 per sq inch) was enough to destroy the lift. That study was part of the body of knowledge that informed subsequent regulation and current best practice.
As someone mentioned earlier, if you attempt flight with contamination you are a test pilot. You may not like the results of your ad hoc experiment, and if not you probably won’t be around to publish your results.