I have Googled and the only answer I can find is 'back with white' which wont work (the where pixels aren't fully opaque the white whill show through).
So, I have some elements in Photoshop set to print as Spot colours via Spot Channels. When I bring this file into Illustrator, it shows as overprrinting. Is there a way to stop them overprinting? If they were CMYK they would knockout by default... that I all I want of these Spot channles.