Model engines generally have liners. Only a handful are designed without liners. Chrome plating has been around for a long time and is very reliable. There are other technologies in use today. Modern manufacturing processes provide for round and square bores in liners or crankcases. I have a Magnum .91 fours stroke with a true chrome bore on the bench several hundred hours on it and the bore is almost untouched< it has a ground finish, BTW. OS liners are nickel plated today. I've never heard of a four stroke liner peeling, but the two strokes sometimes do. I laugh at the new Acura commercials talking about Nikasil as if it was new. Model engines are rarely "rebuilt". When the wear out they are either scavenged for good parts, given away, or parts are just replaced. The only time anyone rechromes is when parts just can't be had and they can't part with the engine. The time involved in rebuilding a model engine quickly exceeds it's replacement cost for common engines.

Piston ring gap is dependent on the actual operating temperature of the components. While cast iron has a very low coefficient of expansion, if the ring gets hot enough it will still bind in the cylinder. If .001"/1" bore has proven to work, that's great. Model engines seem to be made to the old .004"/1". I'm sure this gives the manufacturer piece of mind that the ring won't seize during break in.