I had the UP4 on a Spacedeck and was very happy. My feeling now however is that I should have sprung for the 6 because I believe it really would have been better. Not sure how I can come to that conclusion since I have never heard one, but my thoughts are distilled from everything I have heard over the years on these arms. I would add that these days I consider the 4 a poor value. This is what used to be a $1000.00 arm selling for close to $2000.00
