Thank you both for your replies and the information shared. All very helpful, especially given my knowledge and experience with websites.
I've decided to remove my TC red dot and add an Outerimpact mount in place of the rear fixed sight. That, from what I read on the Outerimpact website, will give me many options for red dot sights.
If I can pick everyone's brain again, any red dot manufacturers stand out above others or recommended... or any recommendation for a specific red dot sight?
Thank you everyone for sharing your wisdom!