RE: jeet longer stroke
You would have to ask Dave Shadel or one of the Nelson pilots about that. I have not set up or flown one of the Nelson LS engines myself, so I could not comment on their setup.
My experience...
I only use the head shims to affect engine performance. And I only do any adjustment there if the air temperature is very, very warm. My best Q-500 engine has not been taken apart since Dub sent it to me and it runs like a watch.
Moving the sleeve .010" or .015" or so with a shim does not change the timing to the point where it will affect performance. The only reason I have used liner shims is to establish a correct piston deck height - to compensate for tolerances in the sleeve/case/rod. That is rarely required because the parts Dub produces are pretty much right on nominal dimensions.