I agree on all accounts. I was being facetious with my percentage to make a point that all of the stories about fake overprints are mostly just that, stories. Personally, I have seen about 3-5 fakes in my time. I think they are more difficult to pass off than most think.
No doubt that a more serious effort would have to be undertaken to actually have a printed back. There are actually some unique characteristics of some of the overprinted cards, which I won't go into on purpose, that gives them a bit of added protection as long as you know what to look for. First of all- anything from Ohio is suspect
.