What I normally do is somehow find a way to lift the new light bulb atleast a foot, or more, from what it normally has been. I've seen the REAL BAD effects of not being careful enough with new bulbs. Other than that just gradually lower the bulb maybe an inch per week, or two weeks to be extra nice to the coral, until it is sitting where you orignally have your bulbs from the tank.

Changing the light duration from 8 to 5 hrs, in my opinion, won't really make a difference to the acclimation, I could be wrong. I would think if a coral is going to be burned it could happen in just a few minutes, but you do have a good point about making the time less for the bulbs to be on. I guess thinking of how we sunburn, the longer you are out in the sun the worse the burn. But if you are under some really intense UV index rays I'm sure burning occurs within a few hours already. I guess to be extra careful using a shorter light period for acclimating won't hurt anything.

I think that is what you are getting at.??