I guess that brings us back to original post, that I interpreted "Just try if you can!" . So I am pushing my envelope further, but I try if the ring groves in the piston do the job for now. The piston rings are postponed, but not forgotten."because they can".... even if it takes hours of labour and experimenting to get it right.
So do not feel discouraged or "doing it wrong" for now.
I recently saw some cast iron blanks lying in a pulley and gear shop. The blanks are maybe 2" diameter and 10" long. Would that be worth to try to make a cylinder or pistonrings out of this kind of material? I would guess they sell it for a reasonable price.