This is one of the reasons I chose NOT to install a Holosun on my Hellcat. Great sight. But you need a baseplate, which raises the sight. No chance of even the tiny 507K being able to cowitness with the irons. Some don't want the cowitness, others do. I fall into the latter category of those who want iron to cowitness thru the glass. But when I looked at the Holosun it will mount easily on a baseplate and there is no modification to the gun. So if you want the Holoson, add a baseplate, or you can find down our slide to instal the Holosun. I'm not doing that.Just picked up a Hellcat Pro. Want to put a Holosun Optic on it. Was informed I would either need to buy and install a plate or file off the two front nubs that will interfere. Questions are 2. What are the pros / cons of filing the nubs off? Does the additional plate create any issue?