Just to be sure what you are experiencing...
I am having trouble seeing a loader digging in when moving backwards in float, unless the bucket is tilted down fully perhaps.
And in that case, you would be offering a chance to bend you cylinder rods if you hit something solid when moving backwards...since the rods would be fully extended and would be in compression mode if the bucket lip hit an obstruction.
So what exactly are you doing when "backgrading" with your bucket? Moving in reverse? Bucket curled fully down. OR?
With tractor stopped, i put the joystick to full forward, and then punch it, the bucket hits the ground with a thump and stops. I curl the bucket up, bucket lip facing up and start reverse. I understand the danger of putting the front lip of the bucket contacting the ground.
If i don't float, i simply put the bucket as close to the ground without touching, and curl the bucket up, and start reverse and adjust the loader to grade the gravel.
Does that sound acceptable? Sorry i am still new to operating. Appreciate all the help i could get.