Electric r/c sounds like the way to go for that model. You could go with rubber but, with those short nacelles I don't think you would get much of a flight.
Besides the balsa may not be the lightest. YOu can check the date of manufacture by looking at the backof the decal sheet. Mosquitos are great looking airplanes. ONe thing I like about a balsa model Mossie is that the real airplane was made of wood also. HOw about posting your build on virtualaerodrome?