The new BME 55 soon to be released will have a significant weight advantage compared to these others in the 50cc class. That is providing they come out soon and you can get one.
BME 55 is 34-36 ounces depending on the carb used. Backplate mount and side reed valve induction. 24x8 bolly prop at 7200 rpm on stock muffler. 6500 rpm on menz 24x8 and stock muffler. Tuned mufflers add 600+ rpm. Cost is 579.00 with Falkon ignition. Available in late April.
http://www.rcuniverse.com/forum/m_37..._1/key_/tm.htm
Think it cannot be done? Just look at the BME110 compared to the 100cc competition.