Sorry but no. There is only one state in the country one can legally exceed the posted speed limit and it isn’t Virginia. Arguing the posted speed may be improper is like arguing a law is unconstitutional. Until such time it is proven invalid, it is valid and all that violate the law may be charged with violating the law. Only if their defense successfully affords them to have their charges dismissed due to the law being invalid can they claim they were not violating the law.
I am not understanding diddly. You are wrong and refuse to admit it. That's all.