Yes its kind of obvious when you think about the mechanics of it, bigger singles have a bigger piston head that weighs more and gets thumped harder by the combustion cycle. So in the twin they are in opposition firing together that imbalance almost cancels itself out and makes it smooth and vibration tends to be of a high frequency low level nature. No matter how smart you are with the single desigbn you cannot get around this fact, unless, you build it with a counterbalance and if you do that you defeat the object of the design (ie weight saving!).

One of the reasons (as i understand it) a single no bigger than 50cc was made for a while was that vibration would be too much of an issue. I mean if you wanted to mabufacturer vibration somehow can you think of a better way than hurling a lump of metal from side to side... I know something about this from personal experience over the years with YS engines that have gone from .90 in size up to now 1.80. While they have got more and more powerfully, incredibly so, the vibration from them has gone from considerable to phenominal, made worse of course by the fact they are four strokes. A YS over 1.40 now can quickly find weaknesses in a wooden airframe, im expecting the DA84 will do the same!