correction...shannons now have 'racing extension'.
this covers damage on your car other than mechanical upto $20k for any racing sanctioned by a racing body (cams etc).
as an illustration, a car insured for $35k will cost around $800 for race only (laid up cover) insurance, and the additional racing extension cover will cost you $2200.
unsure of the excess on the racing extension...likely another 1k or something.