tristanms,
It is true that there are specific requirements for a 30.06 sign such as contrasting colors, letter height and being displayed in a conspicuous manner. However there is no Supreme Court or Appellate Court case law on what happens when a sign is extremely close but not quite right. This means the issue will be decided by a judge or jury. So, unless you don't mind being the test case, we believe the safest bet if you see a sign that is "close" is to take your business to a more gun-friendly establishment.
Thank you for the great question.