Good stuff all
Personal note; have used RA1s and others with 245s - 9x16 and 225s - 7x16 on a stock bodied SC for several years and like the results. 205s and 225 would probably work just as well but I like the look. I don't think you can get away with the larger size wheels and tyres without suspension mods. Street maybe, track no. I also doubt very seriously if a stock HP SC or Carrera would see any advantage with wider/bigger tyres. It would be interesting to hear from those than run 17s and 18s on like cars. Heavier wheels but lighter tyres? Anybody do a comparison?