You can co-witness with a hellcat pro iron sights - Crimson Trace CT-RAD Micro Pro Reflex 1x 5 MOA Green Dot Sights

I purchased this green dot under the promise that it allows you to co-witness with the Hellcat Pro iron sights and thanks to the rear notch, you arr able to. That being said, this optic has an auto-dimming feature that is still a bit too bright (even under complete darkness). It may be because it's a 5 MOA (I am used to a 3 MOA optic), but anyhow, I tried to cover the sensor to see the difference in brightness levels, and the sensor lies at dead center under the glass window (as a comparison, the Swampfox Sentinnel has it on the side so you can cover it with a finger and see the difference, although it does not allow a co-witness with the Hellcat sights). Unlike other reviews where they say it turns off under darkness, I've tested mine after hours of being locked, and it seems to stay on at all times. I have yet to take it to the range, so no word on its performance there, but so far, I would say that if co-witnessing is a high priority, this could be a good option over the Swampfox; otherwise, I would take the Swampfox over it due to a more noticeable auto-dimming and a smaller dot footprint.