I am interested to hear the opinions of some retic keepers here. I am not very versed in designer morphology...but something about this seems off. I would be inclined to say that passing an animal off as a "dwarf" pre-supposes that you are able and, in fact, eager to provide specific information about lineage.
The bottom line is, the only way to even guess how large a retic might be is to see the parents. And, as with most "dwarf" species, their size is related to the locality from which their bloodline originates. Dwarf and superdwarf retics originate from island nations in the Indonesian archipelago and because of isolation, evolved distinct populations that stayed smaller than their mainland cousins due to lack of available food.
Again, there is ALOT I don't know about genetics/morphs, but what I do know is...if I were you, I'd be prepared for that beautiful baby to get really big really fast