What is your definition of "very, very hard". I have an AF1 on my Tiffin Freightliner chassis with a LED light on the dash that indicates when the toad brake is activated.
It takes a fair amount of pressure on the coach service brake before the AF1 is activated, and that is exactly how I want it to perform. I do not want the toad brakes to activate and try and help the coach slow down in normal driving situations. I only want it to give me extra braking force in a panic type stop.
However if you still think it isn't operating correctly I would suggest posting your question on the Tiffin RV Network forum TiffinRVNetwork
There are many PowerGlide owners with AF1 systems that would be glad to share their knowledge.