I’ve been reading up on the differences. My Aero M4E1 has fold down BUS so the “uncluttered field of view” is a moot argument. My BCM has a fixed FSB, I’ve been shooting it with an absolute co-witness mount for 8 years without issue so it’s obviously a non-issue as far as I’m concerned. I will try a lower 1/3 on my next build because I’m planning to use fixed sights on it.