BBX slipper clutch- what gives?

[Smokescreen38 212]

I would like to think that after building about 20 kits, I’d know what I’m doing but I keep coming back to you guys with questions. 
 

I don’t have a lot of experience with slipper clutches.  I attempt to follow the install instructions and tighten against the spring accordingly.  After my first drive with the BBX, I could tell that it was slipping a bit.  Rather than stopping right there, I continued my drive, trying to accelerate gently and just cruise with it.  After this, it got put away while I built other stuff over the winter. 
 

I busted it out today and attempted to finally set the clutch properly.  I followed the “hold the wheels and gently throttle up” technique, looking for the front wheels to come off the ground before slipping.  It doesn’t appear that this point exists. 
 

What I find is that it will slip slightly too much to pull up the wheels.  A tiny, tiny bit tighter and the diff makes the grunting noise that tells you the clutch is too tight. 
 

What am I doing wrong?  Did I damage something by driving (gently!) with the clutch too loose? 

Thanks for any help! 

[Otis311 421]

Is your ball diff tight enough? That grunting sound may be the ball diff barking.