Has anyone installed the RMSc on their Shield .45? Results? Co-witnessing with the front sight? Thinking about picking it up for my edc (low light in the middle of the night/might not have my glasses on)......

I have the Shield RMS on my Shield 9mm. Awsome! Yes, there's a wee bit of overhang but not a problem. The RMSc is specifically designed for the M&P shield and the G43 according to Shield. (UK)
If you'll contact Lone Wolf (they did mine) they'll do a "Race" milling on your Shield (Less than $100) and even sell you a RMS
for $349. I don't know if they're selling the RMSc. They weren't when I had mine done about five months ago. The RMS doesn't have to be removed to change batteries. The RMSc does.
These are fantastic reflex sights. I have a Romeo 1 on my P320. Like it but__I prefer the Shield RMS. Zero it in once and forget it.
There's no buttons on the RMS. (Or the RMSc)
Brownness carry both the RMS and the RMSc. ($400 though)
You don't have to buy the sight from Lone Wolf. I did to save $50.
The Race mill job will remove the rear sight forever. I've found I don't need it. Oh! You'll be able to co-witness the front sight. There's a notch on the Shield in place of the original rear sight.
Hope this helps.
And__it nice to to leave the RMS on constantly. (2-3 years battery life) The Shield RMS's dot adjusts automatically to the atmosphere, instantly. I chose the large dot size__for SD situations only. You might prefer the smaller dot one since the dot adjusts the brightness for you.
Stay safe
Poli Viejo

P.S.
That's Brownells. Oh, if you call Lone Wolf__feel free to mention me,
Capt. Byron Horn. I did so much back and forth with them we became in-laws, I think. I was trying to persuade them to order some of the RMSc ones. However, the RMS fits nearly perfect with hardly enough overhang
it's no issue.
Turn around time may be only a week too!
Stay safe
Poli Viejo