my theorie is that the mack super snow pattern occupies more than one position in their genetic makeup , tug snows must have a mutated chromasone at the same position as a mack snow and when two mutated alliets occupy that position you get super snows, but tug snows must lack the other mutation hence tug x tug only yields tugs not supers
In My breedings with these two morphs in two eggs out of every clutch one egg always hatched out as a super snow and the other hatched out looking like a tug, that is breeding a super snow to one of my TUGsnow females and I've done it twice and thats a total of 22 eggs and every clutch was one ss and one TUG looking snow, Hope this helps