I think rings are never over sized
If u replace ur piston with the over sized piston then u have to install the ring set of that over sized piton
( in cg125 100 k piston pe 100 k ring 150 k piston pe 150k ring )
Here we use the original piston as we install the new liners (for more surety) bcoz as per vernier reading our pistons were accurate
and as per piston size we use the original Mitsubishi mini pajero' ringsets as they are compatible,
In the ringset we just take care of the oil clearance as per manual 0.15-0.3 mm
We use the clumps on the rings just to compress them to put in the cylinders
Please dont hesitate to ask or to share
may be any sharing would be helpful for us for me in the future
we have to support each other