you would gain some "brightness" at the ends of the tank by removing some of the optics but you would reduce the amount of light being delivered in the center of the tank and not really gain a usefull amount for coral growth in the dark areas.
Raising the fixture might be a better option, if you'r not at full power then I'd go this route, but you'll have a lot more light spilling out, same as removing optics really.
Now if you don't have things running at full power presently I would just remove all the optics, that should give you enough total spread and light power for the entire tank. Leaving some of the optics on will give you a very hot spot in the middle of the tank, which might be okay depending on your coral placement but would make the light levels very uneven over the lenght of the tank, IMO