I reached out to Freedom Gorilla to see which optics would fit my new Kimber 1911 Custom Next Generation pistol in 45 caliber.  I already have a Holosun 507K X2 green dot (MCS version) on my Sig Sauer P365 Xmacro, and I love that.  I bought the Kimber in part due to it being optics ready but as a newer pistol, there wasn’t a lot of info available to confirm which specific optics might work (beyond mentioning the included RMR style plate),  I got an immediate reply from Jordan (the lead Customer Service Tech), who then communicated with me back and forth multiple times until I made my choice and even after I got it.  I was impressed by the instructional videos made by Freedom Gorilla, the prompt service (also including processing/shipping/etc, which was very fast) as well as the personal touch offered by Jason.  Since I have a red-green color deficiency, we briefly discussed getting the Holosun gold dot version, but I really wanted the ACSS Vulcan and since I already knew that my other green dot optic worked well for me, I chose to go for the green dot version of the 507C X2 ACSS Vulcan.  
As to the optic itself, it fit very nicely after I figured out I had to use the “T nuts” and screws that came with the Kimber (no instructions from either Kimber or Holosun) in order to mount the optic to the plate that also came with the gun.  I mounted the plate to the gun first, then figured out the T nuts had to go in underneath the plate first to be able to mount the optic to the plate, so I had to remove the plate, add the T nuts, then reinstall it (not a big deal though)   I love this version of Holosun, the ACSS Vulcan, and would even consider swapping out my MCS X2 version if it was made in a smaller 507K version. My Kimber 1911 is single stack and fairly narrow, so the optic sticks out just a bit on the sides despite fitting nicely overall. But I love the big circle reticle as well as the triangular chevron.  It was very accurate right out of the box. I tried the iron sights just once before adding the optic, and they seemed off a bit, but I did not adjust them as I was planning to add the optic regardless.  The big circle works as advertised. I can more quickly and easily find the center than I can with my other MCS version, although admittedly only marginally so after getting used to both. I do need to adjust the brightness at times despite the auto adjusting feature. At an indoor range, it is a bit too bright for me so I get some haziness from the chevron, but outdoors that is not bright enough.  Still functional just not ideal for me, and it’s easy to adjust the brightness   The chevron is easy to work with and to sight in.  With my other Holosun optic (MCS 507K X2), I use the smallest dot (2 MOA) for sighting in but then use the slightly larger 32 moa circle for shooting. Since that is on my carry gun, I have chosen to place that circle directly on the target rather than just below it to make it faster, perhaps at some slight expense of accuracy. The Kimber 1911 with the ACSS Vulcan is not planned for carry, just for range use, and so far I love it, but think it would also be great for carry purposes. 
The “shake awake” feature is great, always on when I pick it up. I got the Sig Sauer Romeo zero Elite optic that was available included on my wife’s Sig P322, but it does not have that shake awake feature.  Meaning it has auto off, so the optic shuts down after about 10 minutes, but you then have to manually press a button inside the optic to get it back on, which is not ideal for home defense or even carry situations. Or even at the range it you’re not shooting that gun for a while. And if you have large fingers (or fingernails) it can be hard to press the on button while not touching the inside of the optic.  (I cut off some wooden golf tees to use as a tool to be able to press the button without touching the optic and while still being able to see through the optic to see the red dot to check the functions, but also far less than ideal to have to do that). Will likely swap that out for another Holosun.  Leaving the optic always on (for the Sig Romeo) will delete the battery, which unlike Holosun, is under the optic so I have to remove the optic from the gun to change the battery, which is also less than ideal.  I think Sig now has newer and improved versions of their Romeo optics but I can’t recommend the Elite option.  
No comment on the solar failsafe as I haven’t had the optic long enough for the battery to start running out of juice.  
Overall, very happy with both the Holosun X2 ACSS Vulcan green dot optic and the service provided by Freedom Gorilla. Thanks!