Hehehe, i think engines with a larger stroke make less flutter because they travel more than those with a shorter stroke, causing the ring to hit the "edges" and bounce back, see what im saying? it like shaking a can of juice for example. If you shake in small quick shakes, the juice just touches the ends, but if you make the shakes bigger like the Monkey Dance (lol?) they really hit the ends of the can. Im no expert on 1:1 engines, just a fair bit of knowledge behind them.