OK, so Zayne is a pain. But just how much of a pain? How does his Karmic Luck tie in with his cortosis guantlets? I know that if there is an even roll for initiative, he gets a -4 to rolls, but if there is an odd roll for initiative, he gets a +4 to rolls. So when he makes a save, with the -4 for example, and he rolls an 11, he misses his save. But if he gets the +4, he makes a save with a 7 or higher. This makes sense so far, right? It gets tricky when you make a lightsaber block save and roll a 14. Does the roll count as an 18 for his gauntlet save? I realize that usually it has to be an exact roll of 18 or higher for the ability to work, but the flip side is that if you roll an 18, but have the -4 going, does it not count as a gauntlet save? Also, can you choose which mettle you use when he has both? Nomi Sunrider of course gives allies mettle (whether they have the Force or not), so when you need to reroll with Zayne, can you choose Nomi's version of mettle or are you stuck with the crapy Karmic mettle (which killed my Zayne last time I played him)?

I know that they don't stack, but I want to know if you can choose to use one or the other.

Actually the two mettle's do stack as they are different names..thus different abilities.

That is incorrect. They are different SAs, thus stack with each other. In fact, both are exceptions, as the full defination states that they stack with themselves (only useable if you can reroll twice).

As for Cortosis Gauntlets, it looks for the result, not the number rolled. So, if on an odd init, you can trigger it on a roll of 14, and can never trigger it on an even init, since the most you will get for your result is 16. Mettle and Karmic Mettle would also figure into the result if you were some how able to spend a FP to reroll Zayne's Block save.