Sorry for delay in replying, If we breed a Dark Sun with a normal it will not guarantee a single gene Dark Matter. It will guarantee that all the offspring are either het Dark Matter or het Albino, Dark Sun is a visual dbl het like a Crypton or a Candino.
So if you were to breed a Crypton to a normal you get either het Cryptic or het Clown but no visuals.
We have breed a Dark Sun to a Pinstripr Pied and as suspected we produced normals and Pinstripes that are all dbl het Pied Albino or dbl het Pied Dark Matter, we have just proved out one of the males as dbl het Pied Dark Matter in a recent clutch.
You are correct in that we can shed test all the offspring produced from a Dark Sun for Albino and any that come back negative will be het Dark Matter.
We have had a few come back negative for Albino and these are now labeled as het Dark Matter.
we have done Dark Sun to Dark Sun pairings and we have seen a difference in appearance of the offspring but by when we have bred them they have all so far proved out visual double het (just bad luck)
The biggest thing for us this year was producing Dark Suns from pairing a BP Albino to one of the dbl het Pied Albino/Dark Matter offspring and the dbl het proved out to be dbl het Pied Dark Matter, proving that the gene is allelic with Albino/Candy.