It's safe enough, well it's the onlything we can really do as of yet
20% is a safe number to use. Webmasters should not worry about it, it happens, it even happens to the owner of the paysites. Can't bitch about it as it's part of life currently.
I know if we can figure out the issue we will tell people how to fix it. As soon as they do I make more money, ofcourse i'm going to tell others
BTW, Online Banking uses POST methods which is a forced var pass through if the var is empty it doesnt pass. Its fail rate is VERY low. Same thing when you send to your processor you use a POST method, wont post without the vars if you make it do so.