Koetsu's work very well on a Morch UP4 - better than on a Ittok and waaay better than on a Rega.
I ran my Rosewood on a yellow dot for a while. It didn't sound bad with the yellow dot, but the sound has improved a lot since I changed to a blue dot. Bass seems a lot tighter and deeper. Mids also seems more detailed and captivating - it seems more attention gabbing if that makes any sense to you. You can just hear the cart is happier on the blue dot.
My Koetsu also seems happiest with the armwand totally parallel with LP i.e. horisontal with no slope towards pivot or cart. I run at 2 grams even.
Regards
Paul