Facetsesame is the man to ask. He had SP manufacture Round 5 compatible doubleshot ducks and hashbangs in Honey Sphericals Extras. It's doable, but chaotic!
Perhaps SP rejected 7bit's files because they couldn't open them in Adobe Illustrator? I think that's what they use. It is *vital* to ask them for screenshots of how they see your files. I remember there was trouble. And SP will, amazingly, manufacture total garbage without bothering to check with you. You must lead the QA.