Having a complete re think on the upgrade. I'm researching the possibility of converting a Tern or a Dahon. Front hub would be obvious and easier but I'm thinking rear wheel would be the better option. The 20 inch wheel is skittish enough without adding a driven motor to it. So the thinking at the moment is to get a 7 or 8 speed gear to address the issue of a taller gear and maybe up the power to 500w. Also looking into battery types too. I've been an avid RC modeller and have been using lipo batteries for years, but maybe too heavy?