I don't understand rule H6. I've never read rule H6 and don't really know what you're referencing there.
It's a little puzzling to have 75% of transactions handled by five banks. A lot of payees would fall into the category of municipalities, credit cards, or whatever--large respectable institutions. To not have those transactions clear instantaneously between post and payment, I'm hard-pressed to understand what the issue is here when we are a very wired country.