[DarG]

I used those small reflectors with 4 rows of T5. With the T5's onm the lighting looked very even. With the halides only, you could see that it it was very bright directly under and around the area of the halide bulbs and that it wasnt as bright as you moved away from the center. You dont see shadows or dark spots, you see what sirreal shows in his picture and it is fairly subtle when looking at the full size tank. A casual observer wouldnt even think about it but you can visually see the gradient. It wasnt difficult to see if looking at the area right under and around the bulb compared to the ends of the tank. If one has a par meter to measure the differences, I know there would be a big difference.
I think that that how the aquascaping was done and also the colors and type of rockwork would impact how noticeable the gradient would be.

As far as the differences between the little reflectors and the Reef Optix, I can see it in Sirreals picture comparing the middle with the two ends. Assuming the bulbs are the same, the center area appears brighter overall and uniformly lit.

I thought the 75 gallon was 18" wide but I guess that there are different dimensions of 75 gallons. I could get the Lumenmax over my 90 (18" wide) with a T5 in front and in back and the outer edges of the SLR reflectors are just inside of the front and back inside rims of the tank. So the bulbs themselves are centered maybe and inch and a half inside those inner rims. It works fine for supplemental lighting. It only looks strange if I use two very different color T5 lamps which would be expected with having two flourescents seperated by almost a foot. If I use, for example, a Blue plus in back and a ATI pro color in front, you can see that the front and back of the tanks have a slightly different tint. But if I use a blue plus and a super actinic, for example, it's much more subtle. Right now I am using a Fiji pruple and a Super actinic and you cant see a difference in tints at all between front and back.