Myk, for thumb grinds, the Iceberg is definitely not the best 
As for the string change, it was just a little thing - perhaps most people wouldn’t have mentioned it, but I noticed that the string the Iceberg came with would, if allowed to rest on the lower half of the yoyo as it is spinning, tend to move around the yoyo more than I liked due to the spinning and friction - standard stuff. The Kitty String in the same situation didn’t do this quite as much. Of course, the easy cure for either is just keeping the string taut, but like I said, its just a little icing on the cake.
I should add that the finger spin problem was never a matter of having a good finger spin going, and then the yoyo would fly back. It was a matter of the yoyo flying back while it was moving toward the finger, or immediately after landing on the finger.
As far as the bearing and bearing seat, I’m referring to sanding the sides of the post of the bearing seat. Maybe my terms weren’t accurate enough.
Read the last few posts on the topic I started on the N12 (link below) where YoyoGarrett’s advice re: sanding cured it’s problem. He includes a pic of how/what to sand. I followed the same procedure with the Iceberg. The sanding helped it very much, but not completely. I then changed the bearing, and after that, everything was great (btw, I tried changing to fresh, clean bearings prior to sanding, but it didn’t really help much).
The first thing Garrett said was, “I’ve had this issue with a couple yo-yos before that had such a tight bearing seat it wouldn’t allow the bearing to spin properly.”
Sanding the vertical post of the bearing seat eliminated something that was slightly interfering with the bearing, causing it to be responsive in certain situations.