Saving with an actual alpha channel doesn’t fix the problem. And the matte can’t really be choked as it gets to thin and starts to deteriorate. Playing with the color and delta settings changes the choke settings a bit, but it’s fairly unpredictable and seems unreliable.
I’m pretty sure the photoshop format isn’t really to blame, as it works with pretty much every other graphic app out there. It’s c4d that doesn’t interpret it’s transparent backgrounds properly.
Is there a way that a fully vector illustrator file could be used with a transparent background instead?