Piston clearance is measured at the skirt, 90* to the pin, which you cannot get at in a sealed block. If you are feeling a tight spot it is most likely the magnet passing the coil, it often feels like a bind.
It had better not be the magnets at halfway down the cylinder...
You could also be feeling the harsh rod angle - reverse the rotation and see if it has as much resistance pulling the piston down the cylinder at that same spot.
I haven't noticed any difference in cylinder clearance or noticeable difference in resistance/drag. I sure hope not as they take forever to break in and free up as it is!
Run it, run it, and run it some more.
Freshen the head and you're good to go some more.
The piston ring tension is very high on these engines.
Most of the tension and therefore the resistance to turning comes from the oil ring expander.
You can use a beam type inch pound torque wrench to compare the force to turn over a new engine compared to a used engine.
If we were allowed to refresh these engine on of the first things most people would do is reduce that tension.
If you have another engine that you can experiment with put it temporarily together without any rings on it and turn it over.
Then put it together with the rings on the piston but leave the oil ring expander on the bench.
All you need is a scant 1/4 teaspoon of the finest TIM100 yellow label for one track session. Mix with oil and add to the crankcase The grit works it's magic then breaks down to nothing in short order, then just change the oil.