I would look at the 55 as something that's not going to happen. There's nothing at all wrong with either the design or the performance, but the developer feels that there are probably enough 50cc class engines already vailable and therefore can't justify another engine in the same calss, regardless of any differences in weight or power.

It's pretty hard to argue the point. Just how many people would jump on a new design for just a couple of ounces of weight difference while tossing in the never ending power debates? If you can't sell a thousand or more in the first production run it's not worth the cost and effort in the long run.