Hi Dave, that dimple under the rocker is definitely noticeable as you can kick it off to one side a bit and feel the clearance change.
According to the dial gauge on the back of the rocker, there's about 0.03mm between the loosest and tightest position.
Right now I'm going to let sleeping dogs lie and keep my fingers crossed it keeps running well. It was weird to actually hear the TX countdown timer go off for a change, it's been a long time since I've heard that when flying this plane.
When the ring is bedded in and I'm happy the engine is "sorted" I'll look at the valve issue a bit closer. Maybe the bottom of the lifters aren't flat anymore and if they rotate to a different position my clearance disappears?? Could be any number of stupid things happening..