I'm not sure what the IVA man will say about the outboard cats... You may have to put a guard on them, as they're bound to get hot - hotter than the muffler boxes.
I couldn't find anything regarding it in the IVA manual, but this caterham builder put some perforated shields on his:
http://www.caterhamr500.co.uk/2014/0...x-exhaust.html
I'd hate for you to do all this hard work only for the man from Vosa to say no on the day.