While not ideal, red dot sights mounted on quality adaptor plates are better than nothing especially when it comes to glocks without milled slides.
This is the case with these three Glock 19s of a Malaysian government Agency.
It took longer than expected because the fit of the Toni Systems adapter plates was so tight that I had to slowly tap them into place and then the screws for the Holosun were too long so I had to file them down.
I did a rough laser bore sighting in the shop and later on this afternoon I will be going down to the police range to confirm zero.
Edit: It rained cats and dogs at the range but we persevered. Managed to zero one but had issues with the other which may need me to go down to a different range tomorrow.