Ok, first time poster here so sorry if this has been spoken about but I couldn’t find anything on it via the search bar.
So I have a question about where exactly to mount the 512 on a rail if the intended purpose was to get it as far forward as possible without leaving the upper receiver. The part that actually clamps down on the rail is pretty small and is highlighted in yellow with a red arrow. The housing of the part that slides over the rail extends a bit further. Pictured is the current location of my optic which is at point “A” where the extended portion of the rails housing ends. My question is that is it fine the way it is or can it safely be moved up to position “B” which is right before the actually clamping section is of the optic if my desire was to have it as far up as possible without leaving the upper receiver.
Thoughts ? Thanks ahead of time.

Welcome to the forum.

You could probably go a little further forward, but I wouldn't have B all the way at the front of the upper receiver. I normally bring it up so that the first bolt in the outer housing is at the front of the upper.

It's an EOTech. Doesn't matter where you put it. You don't really need to have it far forward unless you are sticking a magnifier behind it. If no intention to use a magnifier then I would honestly put it further back for the 512. I find it odd looking to have the battery overhang so far forward.

This is actually an interesting question.  I think it depends on your eyes personally so I would experiment and see what looks the best to you.  I agree that magnifiers do mess with view and I have decided that I dont like the Eotech or the Vertex UH-1 products with a magnifier because for both, it tends to distort or pixilate the reticle for me.  I do not have this problem with Red Dots so I think I may limit magnifiers to Red Dots only.

I had my 512 mounted where yours is for years.  Worked fine but I never used a magnifier.  I had it forward to clear the mag release controls for mag changes.  I used to be a slapper but am more refined now as a pusher.  I pulled my 512 off yesterday to put a RDS on.