The only way to obtain a curved roof spoiler for a Corse is to buy one from Hawk or LB.
It was beyond the wit of anyone making Corse panels in the past to assemble the two halves of the spoiler whilst applying some external means to make the curve while bonding.
You could conceivably buy the flat spoiler off Chris, split it with a slitting blade, and then rebond it using some bridge a gap while on your car and spaced off the roof to the correct curve while it cures.