Wolverine,
You've told us your goals but I'm curious as to the "Why". I assume you aren't shooting competition, or we'd be talking PF, it's not hunting, not for Bullseye, etc. Are you trying to run a finicky subgun?
I'm wondering if you're over thinking this. Whatever your reasoning for NATO spec ammo different powders only give nuanced difference in feel. Why choose to make higher recoiling practice ammo and then search out a slightly lower recoil powder? Especially when you already have 2 powders on hand that fit the bill?