The kingspan will do sweet FA if there is no air gap between the roof and the kingspan. If the eves are open (vented) run a breather felt on the underside of the tin and so it runs off the external side of the eves then put the kingspan back up. Leave 25mm between the tin and breather felt and the felt and kingspan. This may be impossible without taking the roof off, but with out seeing it, it hard to tell. You may be able to pin it to the underside of the rafters?