Fat Bob's question

Hi all, I plan to buy a Fat Bob's lift soon but I keep hearing about some people not being happy because the rear sags down more than the front. Is there any way to know if this will happen to me or is it just luck of the draw?

 

The rear was lower on mine after the lift but they said it was because I have a topper. They also sent me an additional add a leaf to put in which leveled it out. I had ordered the long add a leaf so maybe there's an issue with the long vs the short.

 

Ok thanks. That was another question I had. What is the difference between the long and short?