I've been redrilling 5x114.3 wheels. There are few 15s that can fit over rear calipers. I have some used SSRs. The wheels that could fit need the calipers ground for clearance, fortunately in a low stressed area. I have never managed to get a wheel clearance drawing from any manufacturer, so it is suck it and see. 15x8 ET45 with 205/50 feels and handles great, 225/45 should be similar. 15x9 with 245s needs offset of around 32 and that hurts steering feel, but moar grips! Smaller diameter means better acceleration and slight lowering without screwing roll centres. I run 15s for autocross, 16s for daily.