Basic question: forward or rewarward mount?
I notice that some people mount their optic forward, closer to the handguards, and some like the optic to sit farther back, near the rear iron sight.
I kind of like my red dot sitting closer to my eye.
Are there any practical reasons to mount the red dot forward? Is it purely a matter of taste?
The "fight through the ring" style of shooting advocates that an RDS be as far back as possible so you have a wider FOV through the tube, but in my opinion this makes absolutely no sense since the whole concept behind an RDS is that you keep both eyes open while you shoot (and therefore maintain a wide FOV).
With a further forward mounted red dot, less is obscured by the optic while shooting with both eyes open. This has been my experience.
mounted closer to your eye means more forgiveness in your eye's position. You can move your head around more and still see the dot. Mounted farther away allows room for a magnifier to be placed behind it.
mostly, its personal preference. try both, see which is more comfortable and allows you to be faster and more accurate. There is no 'right' way other than the one that makes you shoot better.
Also mounting the red dot optic in a cantilever mount (forward extending mount) ensures that a 3x magnifier can be mounted behind the red dot optic with the most amount of space for mounting. In the picture below you can see that the whole optics setup has plenty of room to be moved forward. That allows you to adjust for best eye relief.
Usually cantilever mounts do not cost much more than a straight vertical mount. Cantilever mounts could be considered as more versatile.
There's nothing wrong with using a straight vertical mount. Even a straight mount should allow you to use flip up BUIS behind most red dot optics. When you search for pics of people using a red dot with a magnifier ... you'll find that most everyone uses a cantilever mount. I'm actually having a hard time finding a single pic of someone using a straight mount on their red dots with a magnifier behind it.
The great advantage non-magnifying holographic sights have over magnifying scopes is there's infinite eye relief. You can mount it as far up the front rail as you like & it will still work. If you like it close to the rear, it will work fine there as well. If you're running a magnifier or night vision, then things get more particular.