Isn't 0-60times and smaller wheels all to do with some inertial energy thing?
the nearer the centre(driveshaft) the weight is, the easier it is to turn.
so either a lighter wheel or a smaller wheel should help acceleration!?!?
think thats the basics of it, some clever sod can explain better,
but if its just for looks/handling 16s would be fine on a wee fiesta,they'll still look big enough!