Jeep,
I currently have an 8" Stealth "Hunter" on my Liberty in combination with my Spot-Hogg "Hogg-it" sight for 3D shooting.........for hunting season I am going to trim it down a bit to a 6" Stealth Hunter and my Spot -Hogg "Real Deal" sight.
The Liberty is so smooth and balanced so nicely it really doesn't need anything too big. I have it set as it is right now becasue of the extra heft and stability the longer one gives me.
If I don't get that same feeling from the 6" I will simply go back to what I am using now.