If you're worried about parallax-give it a shot with your optic like in the video. I'd advise doing this with any optic you use and see what the error is for yourself and understand its affects.
I've been doing this a long time-talking strictly real world I'm not actually sure. I put the reticle into an acceptable hit zone and send it-my brain doesn't really process scope shadow or the Bezel or anything of that nature. As much as i hate to admit it, my days of room clearing with a 203 equipped m16 and an acog really helped set me up for success with optic versatility. I'm sure its happened though. To be honest I put a lot of practice into presentation so while I may not be perfectly square it's most likely only a very small amount off centered. People like to think that in cqb they'll be working positions like a vtac barricade but that's not likely an a whole other topic to tackle.
