I understand what you are talking about the separate allele complexe

Well, I always tought that the black pastel and the cinnamon was the same gene. I tought someone already mixed both and proven them to be the same. I might be wrong...

Also, I heard that some people tryed to mix caramel and normal albino together and got double het. But they never been able to get offspring from those double hets (not proving out) cause most of the eggs don't hatch. Meaning it would be lethal. But that's rumor, since I never saw a post or someone who did it, just some people telling it. But I haven't been around enough for this.