This may not be the case for you but I have had really, really bad luck attempting to light acclimate.
I have a mature (2 year) tank which has been stable and otherwise health for months and months and months. But I simply could not get my acros and monties to survive to reach their final spot in the tank through an acclimation process. Because of my past failures I became even more cautious and incremental in my approach but eventually they would die. I ruled out everything I could think of including PAR, some kind of contamination, faulty tests etc etc.
I bought some frags 3 months ago. I was so disappointed and discouraged I didn't even want to look at the them. I just dipped them and placed them in the final spot I wanted them. No acclimation.
They are not only surviving, they are growing and getting more colourful by the day. You may be a better reef keeper than me and successfully do it but I think there is probably some truth to the idea that each time you disturb the coral, even by just a slight adjustment, is another piece of stress they don't need. Better to rip off the band-aid quickly.