From what I have seen from hatching about 60 SH mack snows I can tell you that they respond to temp sexing just as reliably as any other morph of leopard gecko... That "mack snows are not temp sexable" thing is BS if you ask me...
I agree with Gregg I`ve never had any problems Hatching Mack Snows of the correct Sex Ratio. As well as any Mack Snow Combination I`ve produced Mack Trempers, SSTA, Hypo Snows, etc.