It's not unusual (although disappointing), I've had large rads on a few bikes and they all needed 'WSB' style fairings, meaning the fairings were altered to accommodate the larger radiator in WSB for example. The sporting regs for the silhouette class is +/- 15mmWOW, that is a radiator!! Looks just Stunning though.
Did you contact the rad manufacturer about the fairing issue, it seems a little odd it does not fit? Your say you cut the fairings? Scary!