Why not require it on every trade?
I hope you don't mind me putting in my thoughts....
I choose not to do BOS because it's my gun or my deal. It's none of no ones business other than the person that I'm dealing with, if that person don't want to deal with me then I'll find another deal. I can take any BOS and photo copy it to state whatever I want after it's signed therefore it's not helping anyone. The only way to prevent this sort of thing from happening is to sign it in front of a notary which would probably cause the deal to fail due to having to find one near where the deal will take place. Now at this point everyone might think that the person you're dealing with would be honest enough not to do something I just described, which should mean you should be able to trust the deal to go good without having said BOS. If we (everyone here) have to worry about the petty stuff then there's more problems in our group than I thought. I hope I haven't offended anyone, that is not my intention. Again this is just my thoughts on the subject.